Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F5/00—Compounds containing elements of Groups 3 or 13 of the Periodic Table
  • C07F5/02—Boron compounds
  • C07F5/025—Boronic and borinic acid compounds
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
  • C07B37/00—Reactions without formation or introduction of functional groups containing hetero atoms, involving either the formation of a carbon-to-carbon bond between two carbon atoms not directly linked already or the disconnection of two directly linked carbon atoms
  • C07B37/04—Substitution
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
  • C07C1/32—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon starting from compounds containing hetero-atoms other than or in addition to oxygen or halogen
  • C07C1/321—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon starting from compounds containing hetero-atoms other than or in addition to oxygen or halogen the hetero-atom being a non-metal atom
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/30—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group
  • C07C67/333—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group by isomerisation; by change of size of the carbon skeleton
  • C07C67/343—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group by isomerisation; by change of size of the carbon skeleton by increase in the number of carbon atoms
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
  • C07B2200/00—Indexing scheme relating to specific properties of organic compounds
  • C07B2200/07—Optical isomers
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
  • C07C2523/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of noble metals
  • C07C2523/48—Silver or gold
  • C07C2523/50—Silver
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2531/00—Catalysts comprising hydrides, coordination complexes or organic compounds
  • C07C2531/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
  • C07C2531/24—Phosphines
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2601/00—Systems containing only non-condensed rings
  • C07C2601/02—Systems containing only non-condensed rings with a three-membered ring
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2601/00—Systems containing only non-condensed rings
  • C07C2601/04—Systems containing only non-condensed rings with a four-membered ring
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2601/00—Systems containing only non-condensed rings
  • C07C2601/06—Systems containing only non-condensed rings with a five-membered ring
  • C07C2601/08—Systems containing only non-condensed rings with a five-membered ring the ring being saturated
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2601/00—Systems containing only non-condensed rings
  • C07C2601/12—Systems containing only non-condensed rings with a six-membered ring
  • C07C2601/14—The ring being saturated
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2601/00—Systems containing only non-condensed rings
  • C07C2601/12—Systems containing only non-condensed rings with a six-membered ring
  • C07C2601/16—Systems containing only non-condensed rings with a six-membered ring the ring being unsaturated
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2602/00—Systems containing two condensed rings
  • C07C2602/02—Systems containing two condensed rings the rings having only two atoms in common
  • C07C2602/04—One of the condensed rings being a six-membered aromatic ring
  • C07C2602/10—One of the condensed rings being a six-membered aromatic ring the other ring being six-membered, e.g. tetraline

Definitions

• the Suzuki-Miyaura reaction is a palladium- or nickel-catalyzed cross coupling between a boronic acid or a boronic ester and an organohalide or an organo-pseudohalide.
• Miyaura A. Chem. Rev., 1995.
• This cross coupling transformation is a powerful method for C— C bond formation in complex molecule synthesis.
• the reaction is tolerant of functional groups and has become increasingly general and widespread in its use for coupling of organic compounds. Barder, T. E. et al, J. Am. Chem. Soc. 2005, 127, 4685-4696;
• Peptides, oligonucleotides, and increasingly oligosaccharides can be rapidly and flexibly prepared in the laboratory from readily accessible building blocks having all of the required site- and stereochemical information pre-installed.
• the inherent modularity of many small molecules and the rapidly expanding scope of boronic acid cross-coupling chemistry 2"4 collectively support the notion that an analogous building block-based approach for small molecule synthesis may be attainable.
• unactivated Csp 3 organoboronates cannot be cross-coupled with the same levels of efficiency, site-, and stereo-retention that is now accessible with many of their Csp 2 and activated Csp 3 hybridized counterparts.
• US 8,338,601 (incorporated by reference) and US 2013/0317223 (incorporated by reference), each to Burke et al., disclose methods of performing chemical reactions using protected organoboronic acid compounds.
• the protected organoboronic acid is a MIDA boronate.
• the reaction is a cross-coupling reaction.
• One aspect of the invention is a method for site- and stereo-retentive cross- couplings of an aryl halide with an unactivated secondary boronic acid.
• the method is characterized by mild reaction conditions, operationally simplicity, and the use of an air- stable and commercially available catalyst.
• the method can employ chiral non-racemic boronic acids, which are readily prepared via resolution with a non-racemic chiral substituted iminodiacetic acid (IDA).
• IDA non-racemic chiral substituted iminodiacetic acid
• An aspect of the invention is a method of forming a product represented by
• R R CH-Ar comprising:
• R 1 and R 2 are selected from the group consisting of substituted Ci-C 6 alkyl and unsubstituted Ci-C 6 alkyl; or R 1 and R 2 , taken together with the carbon to which they are joined, form a substituted or unsubstituted C3-C8 cycloalkyl;
• Ar represents a substituted or unsubstituted monocyclic or polycyclic aryl
• X represents halogen
• Pd catalyst represents Pd(0) or Pd(II);
• ligand is P(o-R-phenyl) 3 ;
• R represents C 1 -C4 alkyl
• the secondary boronic acid is achiral.
• the secondary boronic acid is chiral.
• the secondary boronic acid is a racemic mixture.
• the secondary boronic acid is not a racemic mixture. In certain embodiments, the secondary boronic acid has an enantiomeric excess of at least 80 percent. In certain embodiments, the secondary boronic acid has an enantiomeric excess of at least 90 percent. In certain embodiments, the secondary boronic acid has an enantiomeric excess of at least 95 percent.
• the product represented by R 1 R 2 CH-Ar is not a racemic mixture.
• the product represented by R 1 R 2 CH-Ar has an enantiomeric excess of at least 80 percent. In certain embodiments, the product represented by R 1 R 2 CH- Ar has an enantiomeric excess of at least 90 percent. In certain embodiments, the product represented by R 1 R 2 CH-Ar has an enantiomeric excess of at least 95 percent.
• An aspect of the invention is a method of forming an air-stable chiral secondary boronic acid, wherein the air-stable chiral secondary boronic acid is not a racemic mixture, comprising:
• R 1 and R 2 are selected from the group consisting of substituted Ci-C 6 alkyl and unsubstituted Ci-C 6 alkyl; a chiral iminodiacetic acid, wherein the chiral iminodiacetic acid is not a racemic mixture; a weak acid catalyst; and a polar aprotic solvent, thereby forming a mixture of chiral boronates;
• the chiral iminodiacetic acid has an enantiomeric excess of at least 80 percent. In certain embodiments, the chiral iminodiacetic acid has an
• the chiral iminodiacetic acid has an enantiomeric excess of at least 95 percent.
• the chiral iminodiacetic acid is benzylcyclopentyl iminodiacetic acid (BID A).
• the chiral secondary boronic acid represented by formula (I) is a racemic mixture.
• the chiral secondary boronic acid represented by formula (I) is not a racemic mixture.
• the air-stable chiral secondary boronic acid has an enantiomeric excess of at least 80 percent. In certain embodiments, the air-stable chiral secondary boronic acid has an enantiomeric excess of at least 90 percent. In certain embodiments, the air-stable chiral secondary boronic acid has an enantiomeric excess of at least 95 percent.
• An aspect of the invention is a method of forming an air-stable trihydroxyborate salt of a primary or secondary boronic acid, comprising:
• R 2 is selected from the group consisting of H, substituted Ci-C 6 alkyl and unsubstituted Ci-C 6 alkyl;
• R a and R b are selected from the group consisting of optionally substituted alkyl, aryl, and acyl; or R a and R b taken together with the -0-B(CHR 1 R 2 )-0- moiety to which they are attached form an optionally substituted heterocyclic ring consisting of 5-10 heavy atoms in the backbone of said heterocyclic ring, wherein 3-5 heteroatoms selected independently from the group consisting of B, O, and N are present in said heterocyclic ring; and (ii) combining the primary or secondary boronic acid represented by formula (I), an ether, and concentrated hydroxide, thereby forming an air-stable trihydroxyborate salt of a primary or secondary boronic acid.
• R a and R b are selected from the group consisting of optionally substituted alkyl, aryl, and acyl; or R a and R b taken together with the -0-B(CHR 1 R 2 )-0- moiety to which they are attached form an optional
• the method further comprises combining the air-stable trihydroxyborate salt of a primary or secondary boronic acid, a Lewis acid, and a second polar aprotic solvent, thereby re-forming the primary or secondary boronic acid represented by formula (I).
• the primary or secondary boronate represented by formula (II) is achiral.
• the primary or secondary boronic acid represented by formula (I) is a primary boronic acid.
• the primary or secondary boronic acid represented by formula (I) is a secondary boronic acid.
• the primary or secondary boronate represented by formula (II) is chiral.
• the chiral primary or secondary boronate represented by formula (II) is a racemic mixture.
• the chiral primary or secondary boronate represented by formula (II) is not a racemic mixture.
• the air-stable salt of the primary or secondary boronic acid is a chiral air-stable salt of the secondary boronic acid.
• the chiral air-stable salt of the secondary boronic acid is a racemic mixture.
• the chiral air-stable salt of the secondary boronic acid is not a racemic mixture.
• the chiral air-stable salt of the secondary boronic acid has an enantiomeric excess of at least 80 percent.
• An aspect of the invention is a method of forming a boronic acid, comprising the steps represented by:
• R a represents an organic group
• MIDA N-methyliminodiacetic acid
• the organic group is a chiral organic group
• the boronic acid is a chiral boronic acid
• the chiral organic group is a racemic mixture; and the chiral boronic acid is a racemic mixture.
• the chiral organic group is not a racemic mixture; and the chiral boronic acid is not a racemic mixture.
• the chiral organic group has an enantiomeric excess of at least 80 percent. In certain embodiments, the chiral organic group has an enantiomeric excess of at least 90 percent. In certain embodiments, the chiral organic group has an enantiomeric excess of at least 95 percent.
• the chiral boronic acid has an enantiomeric excess of at least 80 percent. In certain embodiments, the chiral boronic acid has an enantiomeric excess of at least 90 percent. In certain embodiments, the chiral boronic acid has an enantiomeric excess of at least 95 percent.
• Figure 1 depicts a scheme for preparing desired and undesired products of cross- coupling of unactivated chiral secondary boronic acids (Scheme 1).
• Figure 2 depicts a scheme for stabilization of an unstable secondary boronic acid and deprotection of the stabilized secondary boronic acid (Scheme 2).
• Figure 3 depicts a scheme for cross-coupling a chiral non-racemic secondary boronic acid with high site- and stereo-retention (Scheme 3).
• Figure 4 depicts an exemplary series of steps for preparing a chiral nonracemic boronic acid from a diastereomerically enriched cyclic boronate via the intermediacy of a stable chiral nonracemic sodium trihydroxyborate salt.
• the series of steps can be applied to any of a range of cyclic boronates to produce boronic acids from cyclic boronates via the intermediacy of stable sodium trihydroxyborate salts.
• R is an organic group.
• acyloxy or "acyloxy group” as used herein refers to means an acyl group, as defined herein, appended to the parent molecular moiety through an oxygen atom.
• alkenyl or "alkenyl group” means a group formed by removing a hydrogen from a carbon of an alkene, where an alkene is an acyclic or cyclic compound consisting entirely of hydrogen atoms and carbon atoms, and including at least one carbon- carbon double bond.
• An alkenyl group may include one or more substituent groups.
• alkoxy or "alkoxy group” as used herein means an alkyl group, as defined herein, appended to the parent molecular moiety through an oxygen atom.
• alkoxy examples include, but are not limited to, methoxy, ethoxy, propoxy, 2-propoxy, butoxy, tert-butoxy, pentyloxy, and hexyloxy.
• alkyenyloxy "alkynyloxy”, “carbocyclyloxy”, and “heterocyclyloxy” are likewise defined.
• alkyl or "alkyl group” means a group formed by removing a hydrogen from a carbon of an alkane, where an alkane is an acyclic or cyclic compound consisting entirely of hydrogen atoms and saturated carbon atoms. In various embodiments an alkyl contains 1 to 20, 1 to 15, or 1 to 10 carbon atoms. In one embodiment an alkyl contains 1 to 3 carbon atoms.
• alkyl include, but are not limited to, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, 2-methylcyclopentyl, l-(l-ethylcyclopropyl)ethyl and 1- cyclohexylethyl.
• An alkyl group may include one or more substituent groups.
• alkynyl group means a group formed by removing a hydrogen from a carbon of an alkyne, where an alkyne is an acyclic or cyclic compound consisting entirely of hydrogen atoms and carbon atoms, and including at least one carbon-carbon triple bond.
• An alkynyl group may include one or more substituent groups.
• amino refers to -NH 2 and substituted derivatives thereof wherein one or both of the hydrogens are independently replaced with substituents selected from the group consisting of alkyl, haloalkyl, fluoroalkyl, alkenyl, alkynyl, carbocyclyl, heterocyclyl, aryl, aralkyl, heteroaryl, heteroaralkyl, alkylcarbonyl, haloalkylcarbonyl, fluoroalkylcarbonyl, alkenylcarbonyl, alkynylcarbonyl, carbocyclylcarbonyl, heterocyclylcarbonyl, arylcarbonyl, aralkylcarbonyl, heteroarylcarbonyl, heteroaralkylcarbonyl, sufonyl, and sulfinyl groups; or when both hydrogens together are replaced with an alkylene group (to form a ring which contains the nitrogen).
• substituents selected from the group consisting of alkyl, haloalkyl
• amino as used herein means an amino group, as defined herein, appended to the parent molecular moiety through a carbonyl.
• arylalkyl or “aralkyl” as used herein means an aryl group, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein.
• aralkyl include, but are not limited to, benzyl, 2-phenylethyl, 3- phenylpropyl, and 2-naphth-2-ylethyl.
• aromatic or "aromatic group” refers to a planar or polycyclic structure characterized by a cyclically conjugated molecular moiety containing 4n+2 electrons, wherein n is the absolute value of an integer.
• Aromatic molecules containing fused, or joined, rings also are referred to as bicyclic aromatic rings.
• bicyclic aromatic rings containing heteroatoms in a hydrocarbon ring structure are referred to as bicyclic heteroaryl rings.
• aryl or "aryl group” means a group formed by removing a hydrogen from a ring carbon atom of an aromatic hydrocarbon.
• An aryl group may by monocyclic or polycyclic and may include one or more substituent groups.
• aryloxy or "aryloxy group” as used herein means an aryl group, as defined herein, appended to the parent molecular moiety through an oxygen atom.
• heteroaryloxy or “heteroaryloxy group” as used herein means a heteroaryl group, as defined herein, appended to the parent molecular moiety through an oxygen atom.
• An aryloxy group may include one or more substituent groups.
• azido as used herein means a -N 3 group.
• chemical transform of a substance means a product of a chemical transformation of the substance, where the product has a chemical structure different from that of the substance.
• chemical transformation means the conversion of a substance into a product, irrespective of reagents or mechanisms involved.
• cyano as used herein means a -C ⁇ N group.
• cyclic pertains to compounds and/or groups which have one or more rings (e.g., spiro, fused, bridged).
• cycloalkyl or "cycloalkyl group” is a subset of alkyl which refers to a cyclic hydrocarbon radical containing from 3 to 15, 3 to 10, or 3 to 7 carbon atoms.
• cycloalkyl include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl.
• a cycloalkyl group may include one or more substituent groups.
• enantiomeric excess means the absolute difference between the mole fraction of each enantiomer.
• the term "functional group” means an atom or collection of atoms in a molecule that are responsible for characteristic chemical reactions of the molecule.
• functional groups in connection with the invention are alkenyl (olefmic) groups. Additional examples of organic groups including functional groups that may be present in a protected
• organoboronic acid are illustrated or described throughout the present application.
• group means a linked collection of atoms or a single atom within a molecular entity, where a molecular entity is any constitutionally or isotopically distinct atom, molecule, ion, ion pair, radical, radical ion, complex, conformer, etc., identifiable as a separately distinguishable entity.
• a group is any constitutionally or isotopically distinct atom, molecule, ion, ion pair, radical, radical ion, complex, conformer, etc., identifiable as a separately distinguishable entity.
• halogen means -F, -CI, -Br or -I.
• heteroalkenyl or “heteroalkenyl group” means a group formed by removing a hydrogen from a carbon of a heteroalkene, where a heteroalkene is an acyclic or cyclic compound consisting entirely of hydrogen atoms, carbon atoms, and one or more heteroatoms, and including at least one carbon-carbon double bond.
• a heteroalkenyl group may include one or more substituent groups.
• heteroalkyl group means a group formed by removing a hydrogen from a carbon of a heteroalkane, where a heteroalkane is an acyclic or cyclic compound consisting entirely of hydrogen atoms, saturated carbon atoms, and one or more
• a heteroalkyl group may include one or more substituent groups.
• heteroalkynyl or “heteralkynyl group” means a group formed by removing a hydrogen from a carbon of a heteroalkyne, where a heteroalkyne is an acyclic or cyclic compound consisting entirely of hydrogen atoms, carbon atoms and one or more heteroatoms, and including at least one carbon-carbon triple bond.
• a heteroalkynyl group may include one or more substituent groups.
• heteroarylkyl refers to a compound having the term “heteroaralkyl”, “heteroaralkyl group”, “heteroarylalkyl”, or
• heteroarylalkyl group as used herein means a heteroaryl, as defined herein, appended to the parent molecular moiety through an alkyl group, as defined herein.
• Representative examples of heteroarylalkyl include, but are not limited to, pyridin-3-ylmethyl and 2-(thien- 2-yl)ethyl.
• a heteroaralkyl group may include one or more substituent groups.
• heteroaromatic or “heteroaromatic group” as used herein means an aromatic group as defined herein, in which at least one carbon atom is replaced by a heteroatom.
• Representative examples of heteroaromatic groups include, without limitation, pyrrolyl, furanyl, thiophenyl, imidazolyl, oxazolyl, thiazolyl, pyrazolyl, pyridinyl, pyrimidinyl, purinyl, quinolinyl, isoquinolinyl, and carbazolyl.
• a heteroaromatic group may include one or more substituent groups.
• heteroaryl or “heteroaryl group” as used herein means a radical of aromatic ring systems, including, but not limited to, monocyclic, bicyclic and tricyclic rings, which have 3 to 12 atoms including at least one heteroatom, such as nitrogen, oxygen, or sulfur.
• heteroaryl groups include, without limitation, aminobenzimidazolyl, benzimidazolyl, azaindolyl, benzo(b)thienyl,
• benzimidazolyl benzofuranyl, benzoxazolyl, benzothiazolyl, benzothiadiazolyl, benzotriazolyl, benzoxadiazolyl, furanyl, imidazolyl, imidazopyridinyl, indolyl, indolinyl, indazolyl, isoindolinyl, isoxazolyl, isothiazolyl, isoquinolinyl, oxadiazolyl, oxazolyl, purinyl, pyranyl, pyrazinyl, pyrazolyl, pyridinyl, pyrimidinyl, pyrrolyl, pyrrolo[2,3- d]pyrimidinyl, pyrazolo[3,4-d]pyrimidinyl, quinolinyl, quinazolinyl, triazolyl, thiazolyl, thiophenyl, tetrahydroindolyl,
• heteroatom means any atom that is not carbon or hydrogen. In certain embodiments a heteroatom is an atom selected from any of nitrogen, oxygen, sulfur, and phosphorus.
• heterocyclyl refers to a radical of a non-aromatic ring system, including, but not limited to, monocyclic, bicyclic and tricyclic rings, which can be completely saturated or which can contain one or more units of unsaturation, and has 3 to 12 atoms including at least one heteroatom, such as nitrogen, oxygen, or sulfur. For the avoidance of doubt, the degree of unsaturation does not result in an aromatic ring system.
• heterocyclic rings aziridinyl, azirinyl, oxiranyl, thiiranyl, thiirenyl, dioxiranyl, diazirinyl, azetyl, oxetanyl, oxetyl, thietanyl, thietyl, diazetidinyl, dioxetanyl, dioxetenyl, dithietanyl, dithietyl, furyl, dioxalanyl, pyrrolyl, oxazolyl, thiazolyl, imidazolyl, oxadiazolyl, thiadiazolyl, triazolyl, triazinyl, isothiazolyl, isoxazolyl, thiophenyl, pyrazolyl, tetrazolyl, pyridyl,
• heterocyclyl groups of the invention may include one or more substituent groups.
• a heteroaryl group may by monocyclic or polycyclic and may include one or more substituent groups.
• hydroxyl or "hydroxyl group” as used herein means an -OH group.
• organic group means a group containing at least one carbon atom.
• organoboronic acid means a compound represented by R - B(OH) 2 , where R is an organic group that is bonded to the boron through a boron-carbon bond.
• phosphinyl as used herein includes -PH 3 and substituted derivatives thereof wherein one, two or three of the hydrogens are independently replaced with substituents selected from the group consisting of alkyl, haloalkyl, fluoroalkyl, alkenyl, alkynyl, carbocyclyl, heterocyclyl, aryl, aralkyl, heteroaryl, heteroaralkyl, alkoxy, haloalkoxy, fluoroalkyloxy, alkenyloxy, alkynyloxy, carbocyclyloxy, heterocyclyloxy, aryloxy, aralkyloxy, heteroaryloxy, heteroaralkyloxy, and amino.
• a "polar aprotic solvent” is a solvent that will dissolve many salts, but lacks an acidic hydrogen; these solvents generally have intermediate to high dielectric constants and polarity.
• Non-limiting examples of polar aprotic solvents include acetone, acetonitrile, dichloromethane (DCM), dimethyl sulfoxide (DMSO), ethyl acetate, hexamethylphosphoric triamide (HMPT), N,N-dimethylformamide (DMF), and
• protected organoboronic acid means a chemical transform of an organoboronic acid, in which the boron has a lower chemical reactivity relative to the original organoboronic acid.
• sil as used herein includes H 3 Si- and substituted derivatives thereof wherein one, two or three of the hydrogens are independently replaced with substituents selected from alkyl, haloalkyl, fluoroalkyl, alkenyl, alkynyl, carbocyclyl, heterocyclyl, aryl, aralkyl, heteroaryl, and heteroaralkyl.
• substituents selected from alkyl, haloalkyl, fluoroalkyl, alkenyl, alkynyl, carbocyclyl, heterocyclyl, aryl, aralkyl, heteroaryl, and heteroaralkyl.
• Representitive examples include trimethylsilyl (TMS), tert-butyldiphenylsilyl (TBDPS), tert-butyldimethylsilyl (TBS/TBDMS), triisopropylsilyl (TIPS), and [2-(trimethylsilyl)ethoxy]methyl (SEM
• sp 3 hybridization means that an atom is bonded and/or coordinated in a configuration having a tetrahedral character of at least 50%.
• the tetrahedral character of the boron atom is calculated by the method of Hopfl, H. (1999) J Organomet Chem 581 : 129-49. In this method, the tetrahedral character (THC) is defined as:
• THC DA (%) 100 x - ⁇ ⁇
• substituteduent or "substituent group” means a group that replaces one or more hydrogen atoms in a molecular entity.
• substituent groups can include, without limitation, alkyl, alkenyl, alkynyl, halo, haloalkyl, fluoroalkyl, hydroxy, alkoxy, alkyenyloxy, alkynyloxy, carbocyclyloxy, heterocyclyloxy, haloalkoxy, fluoroalkyloxy, sulfhydryl, alkylthio, haloalkylthio, fluoroalkylthio, alkyenylthio, alkynylthio, sulfonic acid, alkylsulfonyl, haloalkylsulfonyl,
• fluoroalkylsulfonyl alkenylsulfonyl, alkynylsulfonyl, alkoxysulfonyl, haloalkoxysulfonyl, fluoroalkoxysulfonyl, alkenyloxysulfonyl, alkynyloxysulfony, aminosulfonyl, sulfuric acid, alkylsulfmyl, haloalkylsulfmyl, fluoroalkylsulfmyl, alkenylsulfinyl, alkynylsulfinyl, alkoxysulfinyl, haloalkoxysulfinyl, fluoroalkoxysulfinyl, alkenyloxysulfinyl,
• alkynyloxysulfiny aminosulfinyl, formyl, alkylcarbonyl, haloalkylcarbonyl,
• fluoroalkylcarbonyl alkenylcarbonyl, alkynylcarbonyl, carboxyl, alkoxycarbonyl, haloalkoxycarbonyl, fluoroalkoxycarbonyl, alkenyloxycarbonyl, alkynyloxycarbonyl, alkylcarbonyloxy, haloalkylcarbonyloxy, fluoroalkylcarbonyloxy, alkenylcarbonyloxy, alkynylcarbonyloxy, alkylsulfonyloxy, haloalkylsulfonyloxy, fluoroalkylsulfonyloxy, alkenylsulfonyloxy, alkynylsulfonyloxy, haloalkoxysulfonyloxy, fluoroalkoxysulfonyloxy, alkenyloxysulfonyloxy, alkynyloxysulfonyloxy, alkylsulfinyloxy
• alkynyloxysulfinyloxy aminosulfinyloxy, amino, amido, aminosulfonyl, aminosulfinyl, cyano, nitro, azido, phosphinyl, phosphoryl, silyl, and silyloxy.
• trialkylsilyloxy or “trialkylsilyloxy group” as used herein refers to a trialkylysilyl group, as defined herein, appended to the parent molecular moiety through an oxygen atom.
• an element means one element or more than one element.
• a reference to "A and/or B", when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.
• the phrase "at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements.
• This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase "at least one" refers, whether related or unrelated to those elements specifically identified.
• At least one of A and B can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.
• isotopic variants of compounds disclosed herein are intended to be encompassed by the disclosure.
• any one or more hydrogens in a molecule disclosed can be replaced with deuterium or tritium.
• Isotopic variants of a molecule are generally useful as standards in assays for the molecule and in chemical and biological research related to the molecule or its use. Methods for making such isotopic variants are known in the art. Specific names of compounds are intended to be exemplary, as it is known that one of ordinary skill in the art can name the same compounds differently.
• ionizable groups i.e., groups from which a proton can be removed (e.g., -COOH) or added (e.g., amines) or which can be quaternized (e.g., amines). All possible ionic forms of such molecules and salts thereof are intended to be included individually in the disclosure herein.
• salts of the compounds herein one of ordinary skill in the art can select from among a wide variety of available counterions those that are appropriate for preparation of salts of this disclosure for a given application. In specific applications, the selection of a given anion or cation for preparation of a salt may result in increased or decreased solubility of that salt.
• Certain protected organoboronic acid compounds comprising a boron having an sp 3 hybridization, a conformationally rigid protecting group bonded to the boron, and an organic group bonded to the boron through a boron-carbon bond; methods of making same; and methods of performing chemical reactions using same are disclosed in U.S. Patent Nos.
• R , R , R , R , and R independently are selected from the group consisting of a hydrogen group and an organic group.
• the protected organoboronic acid is a N-methyliminodiacetic acid (MIDA) boronate; i.e., R 20 is methyl, and each of R 21 , R 22 , R 23 , and R 24 is hydrogen.
• MIDA N-methyliminodiacetic acid
• Protected organoboronic acids according to the foregoing formula may be prepared by reaction of an appropriate N-substituted imino-di-carboxylic acid with the corresponding unprotected boronic acid, as illustrated in the following reaction scheme:
• protected organoboronic acids may be prepared by reaction of N-methyliminodiacetic acid (MIDA) with the corresponding unprotected boronic acid, as illustrated in the following reaction scheme:
• MIDA N-methyliminodiacetic acid
• the protected organoboronic acid may be deprotected by contact with a mild aqueous base, to provide the free boronic acid.
• Certain protected organoboronic acid compounds comprising a boron having an sp 3 hybridization, a conformationally rigid protecting group bonded to the boron, a chiral first organic group bonded to the protecting group, and a second organic group bonded to the boron through a boron-carbon bond; methods of making same; and methods of performing chemical reactions using same are disclosed in U.S. Patent Application Publication No. 2014/0094615 to Burke et al., the entire content of which is incorporated herein by reference. Such compounds are represented generally by the following formula:
• R 10 represents the second organic group
• B represents the boron having sp 3 hybridization
• R * represents the chiral first organic group
• R 21 , R 22 , R 23 , and R 24 independently are selected from the group consisting of a hydrogen group and an org group.
• R* is a chiral group represented by
• R 31 and R 32 are independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, aralkyl, and heteroaralkyl; or R 31 and R 32 , taken together, form a 5-10-membered cycloalkyl or aromatic ring, or form a 5-10-membered heterocyclic or heteroaromatic ring comprising 1-3 heteroatoms independently selected from the group consisting of N, O, and S;
• R 33 is selected from the group consisting of hydrogen, alkyl, cycloalkyl,
• heterocyclyl aryl, heteroaryl, aralkyl, and heteroaralkyl
• n is an integer 0, 1, or 2.
• R* is a chiral group of at least 90 percent enantiomeric excess.
• R , R , R , and R are independently selected from the group consisting of hydrogen and (Ci-C 3 )alkyl.
• R 1 and R 2 , and/or R 3 and R 4 are independently selected from the group consisting of hydrogen and (Ci-C 3 )alkyl.
• R , R , R , and R are hydrogen. In one embodiment, R* is
• R* is
• R* is
• R* is selected from the group consisting of
• R* is selected fr m the group consisting of
• R* is selected from the group consisting of
• R 31 and R 32 taken together, form a 5-10-membered cycloalkyl or aromatic ring, or form a 5-10-membered heterocyclic or heteroaromatic ring comprising 1-3 heteroatoms independently se consisting of N, O, and S.
• R* is
• R* is
• R* is
• R* is
• R* is
• R* is
• Protected chiral organoboronic acids according to the foregoing formula may be prepared by reaction of an appropriate N-substituted imino-di-carboxylic acid with the corresponding unprotected boronic acid, as illustrated in the following reaction scheme:
• chiral protected organoboronic acids according to formula (I) may be prepared by reaction of N-pinene-iminodiacetic acid (PIDA) with the corresponding unprotected boronic acid (V), as illustrated in the following reaction scheme:
• the chiral protected organoboronic acid may be deprotected by contact with a mild aqueous base, to provide the free boronic acid.
• invertive transmetalation 3d and/or an undesired sequence of beta-hydride elimination followed by hydropalladation and reductive elimination from a secondary carbon-palladium bond may cause loss of the stereochemical information present in the starting boronic acid.
• Table 1 Efficient and site-retentive cross-coupling of la. a
• bidentate phosphine ligands 8 resulted in decreased yields and/or no improvement in site-selectivity (entries 5-7), and bulky trialkylphosphine ligands 4a did not yield any detectable product (entries 8-10).
• Buchwald-type dialkyl biaryl phosphine ligands which possess an ipso -interaction between the Pd center and the biaryl moiety on the ligand, 9 and thus could theoretically achieve this goal, are ineffective in promoting the desired cross-coupling (entries 11-13).
• a mechanistically analogous but undesirable ⁇ -hydride elimination pathway that competes during C-N cross-coupling with primary alkyl amines was suppressed by the use of Pd(P(o- tol)3)2, 10 in which the ort/zo-methyl groups on the ligand may sterically block the required open coordination site on Pd.
• An aspect of the invention is a method of forming a product represented by
• R 1 R 2 CH-Ar comprising:
• R 1 and R 2 are selected from the group consisting of substituted Ci-C 6 alkyl and unsubstituted Ci-C 6 alkyl; or R 1 and R 2 , taken together with the carbon to which they are joined, form a substituted or unsubstituted C 3 -C 8 cycloalkyl;
• Ar represents a substituted or unsubstituted monocyclic or polycyclic aryl
• X represents halogen
• Pd catalyst represents Pd(0) or Pd(II); ligand is P(o-R-phenyl) 3 ; and
• R represents C 1 -C4 alkyl
• Pd catalyst represents Pd(0).
• Pd catalyst represents Pd(II).
• ligand is P(o-tol) 3 (i.e., R is methyl).
• the secondary boronic acid is achiral.
• the secondary boronic acid is chiral.
• the secondary boronic acid is a racemic mixture.
• the secondary boronic acid is not a racemic mixture.
• the phrase "is not a racemic mixture” as used herein shall be understood to be equivalent to the phrase “is a non-racemic mixture”.
• the secondary boronic acid has an enantiomeric excess of at least 80 percent. That is, in various individual embodiments, the secondary boronic acid has an enantiomeric excess of at least 80 percent, at least 81 percent, at least 82 percent, at least 83 percent, at least 84 percent, at least 85 percent, at least 86 percent, at least 87 percent, at least 88 percent, at least 89 percent, at least 90 percent, at least 91 percent, at least 92 percent, at least 93 percent, at least 94 percent, at least 95 percent, at least 96 percent, at least 97 percent, at least 98 percent, or at least 99 percent.
• the secondary boronic acid has an enantiomeric excess of at least 90 percent.
• the secondary boronic acid has an enantiomeric excess of at least 95 percent.
• the product represented by R 1 R 2 CH-Ar is not a racemic mixture.
• the product represented by R 1 R 2 CH-Ar has an enantiomeric excess of at least 80 percent.
• the product represented by R 1 R 2 CH-Ar has an enantiomeric excess of at least 90 percent.
• the product represented by R 1 R 2 CH-Ar has an enantiomeric excess of at least 95 percent.
• R 1 and R 2 are selected from the group consisting of substituted Ci-C 6 alkyl and unsubstituted Ci-C 6 alkyl. In certain embodiments, R 1 and R 2 , taken together with the carbon to which they are joined, form a substituted or unsubstituted C3-C8 cycloalkyl.
• Ar represents a substituted or unsubstituted phenyl.
• Ar represents a substituted or unsubstituted polycyclic aryl.
• X is Br
• X is I.
• An aspect of the invention is a method of forming an air-stable chiral secondary boronic acid, wherein the air-stable chiral secondary boronic acid is not a racemic mixture, comprising:
• Ci-C 6 alkyl consisting of substituted Ci-C 6 alkyl and unsubstituted Ci-C 6 alkyl; a chiral iminodiacetic acid, wherein the chiral iminodiacetic acid is not a racemic mixture; a weak acid catalyst; and a polar aprotic solvent, thereby forming a mixture of chiral boronates;
• the resolving is by crystallization.
• the resolving is by chromatography.
• the hydrolyzing is with aqueous hydroxide.
• the hydrolyzing is with aqueous NaOH.
• the chiral iminodiacetic acid has an enantiomeric excess of at least 80 percent. That is, in various individual embodiments, the chiral iminodiacetic acid has an enantiomeric excess of at least 80 percent, at least 81 percent, at least 82 percent, at least 83 percent, at least 84 percent, at least 85 percent, at least 86 percent, at least 87 percent, at least 88 percent, at least 89 percent, at least 90 percent, at least 91 percent, at least 92 percent, at least 93 percent, at least 94 percent, at least 95 percent, at least 96 percent, at least 97 percent, at least 98 percent, or at least 99 percent.
• the chiral iminodiacetic acid has an enantiomeric excess of at least 90 percent.
• the chiral iminodiacetic acid has an enantiomeric excess of at least 95 percent.
• the chiral iminodiacetic acid is benzylcyclopentyl iminodiacetic acid (BID A).
• the weak acid catalyst is pyridinium /?-toluenesulfonate (PPTS).
• the polar aprotic solvent is CH3CN.
• the chiral secondary boronic acid represented by formula (I) is a racemic mixture.
• the chiral secondary boronic acid represented by formula (I) is not a racemic mixture.
• the air-stable chiral secondary boronic acid has an enantiomeric excess of at least 80 percent. That is, in various individual embodiments, the air-stable chiral secondary boronic acid has an enantiomeric excess of at least 80 percent, at least 81 percent, at least 82 percent, at least 83 percent, at least 84 percent, at least 85 percent, at least 86 percent, at least 87 percent, at least 88 percent, at least 89 percent, at least 90 percent, at least 91 percent, at least 92 percent, at least 93 percent, at least 94 percent, at least 95 percent, at least 96 percent, at least 97 percent, at least 98 percent, or at least 99 percent.
• the air-stable chiral secondary boronic acid has an enantiomeric excess of at least 90 percent.
• the air-stable chiral secondary boronic acid has an enantiomeric excess of at least 95 percent.
• An aspect of the invention is a method of forming an air-stable trihydroxyborate salt of a primary or secondary boronic acid, comprising:
• R 1 is selected from the group consisting of substituted Ci-C 6 alkyl and unsubstituted Ci-C 6 alkyl;
• R 2 is selected from the group consisting of H, substituted Ci-C 6 alkyl and unsubstituted Ci-C 6 alkyl;
• R a and R b are selected from the group consisting of optionally substituted alkyl, aryl, and acyl; or R a and R b taken together with the -0-B(CHR 1 R 2 )-0- moiety to which they are attached form an optionally substituted heterocyclic ring consisting of 5-10 heavy atoms in the backbone of said heterocyclic ring, wherein 3-5 heteroatoms selected independently from the group consisting of B, O, and N are present in said heterocyclic ring; and
• the method further comprises combining the air-stable trihydroxyborate salt of a primary or secondary boronic acid, a Lewis acid, and a second polar aprotic solvent, thereby re-forming the primary or secondary boronic acid represented by formula (I).
• the Lewis acid is BF 3 OEt 2 .
• the second polar aprotic solvent is dioxane.
• the primary or secondary boronate represented by formula (II) is represented by formula (III):
• R 2 is selected from the group consisting of H, substituted Ci-C 6 alkyl, and unsubstituted Ci-C 6 alkyl;
• B represents boron having sp 3 hybridization
• R , R , R , R , and R independently are selected from the group consisting of a hydrogen group and an organic group.
• R 21 , R 22 , R 23 , and R 24 each represent a hydrogen group.
• the primary or secondary boronate represented by formula (II) is achiral.
• the primary or secondary boronic acid represented by formula (I) is a primary boronic acid.
• the primary or secondary boronic acid represented by formula (I) is a secondary boronic acid.
• the air-stable salt of the primary or secondary boronic acid is achiral.
• the primary or secondary boronate represented by formula (II) is chiral.
• the primary or secondary boronate represented by formula (II) is represented by formula (IV):
• the primary or secondary boronic acid represented by formula (I) is a primary boronic acid.
• the primary or secondary boronic acid represented by formula (I) is a secondary boronic acid.
• the secondary boronic acid is achiral.
• the secondary boronic acid is chiral.
• the chiral secondary boronic acid represented by formula (I) is a racemic mixture.
• the chiral secondary boronic acid represented by formula (I) is not a racemic mixture.
• the chiral primary or secondary boronate represented by formula (II) is a racemic mixture.
• the chiral primary or secondary boronate represented by formula (II) is not a racemic mixture.
• the chiral primary or secondary boronate represented by formula (II) has an enantiomeric excess of at least 80 percent.
• the chiral primary or secondary boronate represented by formula (II) has an enantiomeric excess of at least 90 percent.
• the chiral primary or secondary boronate represented by formula (II) has an enantiomeric excess of at least 95 percent.
• the air-stable salt of the primary or secondary boronic acid is a chiral air-stable salt of the secondary boronic acid.
• the chiral air-stable salt of the secondary boronic acid is a racemic mixture.
• the chiral air-stable salt of the secondary boronic acid is not a racemic mixture.
• the chiral air-stable salt of the secondary boronic acid has an enantiomeric excess of at least 80 percent.
• the chiral air-stable salt of the secondary boronic acid has an enantiomeric excess of at least 90 percent.
• the chiral air-stable salt of the secondary boronic acid has an enantiomeric excess of at least 95 percent.
• the first polar aprotic solvent is tetrahydrofuran (THF).
• the aqueous hydroxide is aqueous NaOH.
• the ether is methyl tert-butyl ether (MTBE).
• the concentrated hydroxide is concentrated NaOH.
• An aspect of the invention is a method of forming a boronic acid, comprising the steps represented by:
• R a represents an organic group
• MIDA N-methyliminodiacetic acid
• the weak acid catalyst is pyridinium /?-toluenesulfonate (PPTS).
• the first polar aprotic solvent and the second polar aprotic solvent are the same.
• the first polar aprotic solvent is CH3CN.
• the base is NaOH.
• the second polar aprotic solvent is tetrahydrofuran (THF).
• the first polar aprotic solvent is CH3CN, and the second polar aprotic solvent is THF.
• the organic group is a chiral organic group
• the boronic acid is a chiral boronic acid
• the chiral organic group is a racemic mixture; and the chiral boronic acid is a racemic mixture.
• the chiral organic group is not a racemic mixture; and the chiral boronic acid is not a racemic mixture.
• the chiral organic group has an enantiomeric excess of at least 80 percent. That is, in various individual embodiments, the chiral organic group has an enantiomeric excess of at least 80 percent, at least 81 percent, at least 82 percent, at least 83 percent, at least 84 percent, at least 85 percent, at least 86 percent, at least 87 percent, at least 88 percent, at least 89 percent, at least 90 percent, at least 91 percent, at least 92 percent, at least 93 percent, at least 94 percent, at least 95 percent, at least 96 percent, at least 97 percent, at least 98 percent, or at least 99 percent.
• the chiral organic group has an enantiomeric excess of at least 90 percent.
• the chiral organic group has an enantiomeric excess of at least 95 percent.
• the chiral boronic acid has an enantiomeric excess of at least 80 percent. That is, in various individual embodiments, the chiral boronic acid has an enantiomeric excess of at least 80 percent, at least 81 percent, at least 82 percent, at least 83 percent, at least 84 percent, at least 85 percent, at least 86 percent, at least 87 percent, at least 88 percent, at least 89 percent, at least 90 percent, at least 91 percent, at least 92 percent, at least 93 percent, at least 94 percent, at least 95 percent, at least 96 percent, at least 97 percent, at least 98 percent, or at least 99 percent.
• the chiral boronic acid has an enantiomeric excess of at least 90 percent.
• the chiral boronic acid has an enantiomeric excess of at least 95 percent.
• Csp 3 organoboronates (a) Imao, D.; Glasspoole, B. W.; Laberge, V. S.; Crudden, C. M. J. Am. Chem. Soc. 2009, 131, 5024-5025. (b) Sandrock, D. L.; Jean-Gerard, L.; Chen, C; Dreher, S. D., Molander. G. A. J. Am. Chem. Soc, 2010, 132, 17108-17110. (c) Ohmura, T.; Awano, T.; Suginome, M. J. Am. Chem. Soc, 2010, 132, 13191— 13193.
• Pd(P(o-tol) 3 ) 2 and Ag 2 0 were purchased from Sigma- Aldrich. A gift of Pd(P(o- tol)3) 2 was donated by Johnson Matthey. Solvents were purified via passage through packed columns as described by Pangborn and coworkers 1 (THF, Et 2 0, CH 3 CN, CH 2 C1 2 : dry neutral alumina; hexane, benzene, and toluene, dry neutral alumina and Q5 reactant;
• Diisopropylethylamine was freshly distilled under an atmosphere of nitrogen from CaH 2 .
• racemic 2-butyl boronic acid (+/-)-la 710 mg, 5 mmol
• N-methyliminodiacetic acid (MIDA) (2.20 g, 15 mmol)
• pyridinium /?-toluenesulfonate 126 mg, 0.5 mmol
• acetonitrile 16.7 mL, 0.3 M for the borate
• racemic potassium trans- 2-methylcyclohexyltrifiuoro borate 6b (1.02 g, 5 mmol)
• N-methyliminodiacetic acid (MIDA) (2.20 g, 15 mmol)
• pyridinium /?-toluenesulfonate 126 mg, 0.5 mmol
• silica gel 900 mg followed by acetonitrile (16.7 mL, 0.3 M for the borate).
• the reaction was sealed and allowed to stir at 80 °C for 12 hours. After cooling down, the mixture was passed through a pad of silica gel before concentration.
• aryl halide (0.10 mmol), boronic acid (0.20 mmol), Ag 2 0 (70 mg, 0.30 mmol) and Pd(P(o-tol) 3 ) 2 (7.15 mg, 0.010 mmol) were taken up in THF (220 ⁇ ) in a 7-mL vial.
• the reaction was sealed, and stirred at 85 °C for 24 h.
• the mixture was then passed through a pad of silica gel and flushed with diethyl ether before concentration in vacuo.
• the desired product was isolated by column chromatography and/or preparative reverse-phase HPLC.
• Enantiomeric ratio (Br-, 85 : 15, a 88% retention of e.r.; I-, 89: 1 1 , a 91% retention of e.r.) was determined by chiral-GC (CP chirasil-DEX CB Column)
• Enantiomeric ratio (Br-, 92:8, a 94% retention of e.r.; I-, 92:8, a 94% retention of e.r.) was determined by SFC analysis (OD-H Column)
• Enantiomeric ratio (Br-, 97:3, a 99% retention of e.r.) was determined by chiral-GC (CP chirasil-DEX CB Column)
• the e.r. was determined by chiral-GC using a CP chirasil-DEX CB Column (30 m x 320 ⁇ x 0.25 ⁇ ).
• the solid sample present in one of the vials was then immediately analyzed by 1 H-NMR to verify the purity and quantity of boronic acid present at time zero (the NMR assay is described below). After 1 day (boronic acid) or 60 days (BIDA boronates), the solid sample in the second vial was analyzed by 1 H-NMR, again by the method described below, to determine the quantity of boronic acid remaining at the indicated time.
• NMR assay An NMR stock solution was prepared as follows: To a 25 mL volumetric flask was added bromoacetophenone (0.336 g, 1.69 mmol, internal standard for quantification of the boronic acid), tetramethylsilane (1 mL, internal standard for the NMR shifts), and DMSO-d6:D 2 0 95 :5 to a final solution volume of 25.0 mL. To a vial containing solid boronic acid or solid BIDA boronate (see above) was added 1.00 mL of this NMR stock solution, and the resulting solution was analyzed by ⁇ -NMR.
• the mmol of boronic acid or MIDA boronate present in the sample was determined by comparing the ratio of the integrated 4-bromoacetophenone aryl C-H doublets (7.90 ppm relative to TMS) to that of the boronic acid or MIDA boronate C-H signals.
• racemic secondary alkylboronic acids such as la undergo complexation with the chiral derivative of iminodiacetic acid, 8. The resulting
• substrate 11 2.44 g (5 mmol), 10%> Pd on carbon: 1.2 g, 1,4-cyclohexadiene: 4.9 mL (50 mmol), absolute EtOH: 50 mL
• Racemic la obtained from Sigma Aldrich, was combined with DMSO, toluene, and 8 in a round-bottom flask with a stir bar. The flask was fitted with a Dean-Stark trap and reflux condensor. The mixture was stirred at reflux in an oil bath at 170 °C under air with continuous removal of water. After 3 hours, conversion was complete by TLC using 1 : 1 EtOAc:hexanes and KMn0 4 stain. The toluene was removed by rotary evaporation. 200 mL of DCM and 200 mL were added to the resulting DMSO suspension. In a separatory funnel, the aqueous layer was extracted four times with DCM.
• the combined DCM phase was washed with water five times, then once with brine. It was then dried with sodium sulfate and concentrated by rotary evaporation. The resulting solid was dissolved in acetone and passed through silica in a glass frit. The flow-through was again concentrated under vacuum.
• the crude 5, 1 : 1 dr was dissolved in 40 mL of dry acetone with heating. 80 mL of Et 2 0 was slowly added to this stirred solution, causing a white precipitate. This was stirred 10 hours and the solids were filtered. This white solid, 2.55 g, was dissolved in 17 mL acetone. 34 mL Et 2 0 was slowly added, causing precipitation.
• the combined MTBE phase was dried over Na 2 S0 4 and concentrated by rotary evaporation to a volume of 10 mL.
• To this solution was added 106 of 50% NaOH over 1 minute with rapid stirring.
• the suspension was stirred 20 minutes at room temperature, then the solids were collected by filtration through a medium glass frit.
• the solids were washed with 2 mL of MTBE and dried under vacuum at 1 torr for 12 hours to give 12 in 88% yield as a white solid.
• the substrate was added to a round-bottom flask under N 2 with a reflux condensor containing LAH and THF. The mixture was stirred at reflux for 15 hours. Aqueous Rochelle salt and water were added to quench the reaction. The reaction was extracted three times with DCM. The combined organic phase was dried with Na 2 S0 4 and concentrated under vacuum. The residue was filtered through a silica plug with EtOAc and concentrated again to 31 1 mg oil. This alcohol (S)-3-phenylbutan-l-ol (14) was used directly in the next step.

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