WO2012012391A2 - Process for preparing pyrano - [2,3-c]pyridine derivatives - Google Patents

Process for preparing pyrano - [2,3-c]pyridine derivatives Download PDF

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WO2012012391A2
WO2012012391A2 PCT/US2011/044489 US2011044489W WO2012012391A2 WO 2012012391 A2 WO2012012391 A2 WO 2012012391A2 US 2011044489 W US2011044489 W US 2011044489W WO 2012012391 A2 WO2012012391 A2 WO 2012012391A2
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Prior art keywords
compound
alkyl
formula
reagent
dehydrating
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PCT/US2011/044489
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French (fr)
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WO2012012391A3 (en
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Joseph Sisko
Douglas Mans
Hao Yin
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Glaxo Group Limited
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Priority to EP11810260.7A priority Critical patent/EP2595994B1/en
Priority to CN201180035535.7A priority patent/CN103492393A/en
Priority to ES11810260.7T priority patent/ES2574179T3/en
Priority to US13/810,741 priority patent/US8759523B2/en
Priority to BR112013001257A priority patent/BR112013001257A2/en
Priority to JP2013520798A priority patent/JP5762538B2/en
Priority to KR1020137003678A priority patent/KR20130129902A/en
Priority to SG2013004452A priority patent/SG187146A1/en
Priority to EA201390016A priority patent/EA201390016A1/en
Publication of WO2012012391A2 publication Critical patent/WO2012012391A2/en
Publication of WO2012012391A3 publication Critical patent/WO2012012391A3/en

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D491/00—Heterocyclic compounds containing in the condensed ring system both one or more rings having oxygen atoms as the only ring hetero atoms and one or more rings having nitrogen atoms as the only ring hetero atoms, not provided for by groups C07D451/00 - C07D459/00, C07D463/00, C07D477/00 or C07D489/00
    • C07D491/02—Heterocyclic compounds containing in the condensed ring system both one or more rings having oxygen atoms as the only ring hetero atoms and one or more rings having nitrogen atoms as the only ring hetero atoms, not provided for by groups C07D451/00 - C07D459/00, C07D463/00, C07D477/00 or C07D489/00 in which the condensed system contains two hetero rings
    • C07D491/04—Ortho-condensed systems
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D491/00—Heterocyclic compounds containing in the condensed ring system both one or more rings having oxygen atoms as the only ring hetero atoms and one or more rings having nitrogen atoms as the only ring hetero atoms, not provided for by groups C07D451/00 - C07D459/00, C07D463/00, C07D477/00 or C07D489/00
    • C07D491/02—Heterocyclic compounds containing in the condensed ring system both one or more rings having oxygen atoms as the only ring hetero atoms and one or more rings having nitrogen atoms as the only ring hetero atoms, not provided for by groups C07D451/00 - C07D459/00, C07D463/00, C07D477/00 or C07D489/00 in which the condensed system contains two hetero rings
    • C07D491/04—Ortho-condensed systems
    • C07D491/044—Ortho-condensed systems with only one oxygen atom as ring hetero atom in the oxygen-containing ring
    • C07D491/052—Ortho-condensed systems with only one oxygen atom as ring hetero atom in the oxygen-containing ring the oxygen-containing ring being six-membered
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K31/00—Medicinal preparations containing organic active ingredients
    • A61K31/33—Heterocyclic compounds
    • A61K31/395—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins
    • A61K31/435—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having six-membered rings with one nitrogen as the only ring hetero atom
    • A61K31/4353—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having six-membered rings with one nitrogen as the only ring hetero atom ortho- or peri-condensed with heterocyclic ring systems
    • A61K31/436—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having six-membered rings with one nitrogen as the only ring hetero atom ortho- or peri-condensed with heterocyclic ring systems the heterocyclic ring system containing a six-membered ring having oxygen as a ring hetero atom, e.g. rapamycin
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P31/00—Antiinfectives, i.e. antibiotics, antiseptics, chemotherapeutics
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D491/00—Heterocyclic compounds containing in the condensed ring system both one or more rings having oxygen atoms as the only ring hetero atoms and one or more rings having nitrogen atoms as the only ring hetero atoms, not provided for by groups C07D451/00 - C07D459/00, C07D463/00, C07D477/00 or C07D489/00
    • C07D491/02—Heterocyclic compounds containing in the condensed ring system both one or more rings having oxygen atoms as the only ring hetero atoms and one or more rings having nitrogen atoms as the only ring hetero atoms, not provided for by groups C07D451/00 - C07D459/00, C07D463/00, C07D477/00 or C07D489/00 in which the condensed system contains two hetero rings
    • C07D491/04—Ortho-condensed systems
    • C07D491/044—Ortho-condensed systems with only one oxygen atom as ring hetero atom in the oxygen-containing ring

Definitions

  • the present invention relates to pyrano-[2,3-c]pyridine derivatives and methods for their preparation.
  • 3,4-Dihydro-2H-pyrano[2,3-c]pyridine-6-carbaldehyde disclosed in WO2004058144, is characterized by the following Formula (VIII):
  • Pyrano-[2,3-c]pyridine derivatives have shown promise as useful intermediates to compounds useful for treating bacterial infections.
  • Previously disclosed methods for preparing pyrano-[2,3-c]pyridine-6-carbaldehyde are arduous, requiring many steps using expensive starting materials and resulting in unsatisfactory overall yields. (See
  • the present invention is a process comprising dehydrating a compound of Formula (I):
  • R 2 is Ci-C 4 -alkyl
  • R 3 is H, Ci-C 4 -alkyl, benzyl, -phenyl-(R 10 ) x , or -Ci-C4-alkyl-COO-Ci-C 4 -alkyl;
  • each R 4 is independently H, or Ci-C 4 -alkyl
  • each R 5 and each R 6 are independently H, Ci-C 4 -alkyl, -0-Ci-C 4 -alkyl, or -S-Ci-C 4 -alkyl;
  • R 7 is R 8 or -CH 2 -R 9 ;
  • R 8 is H, Ci-C 4 -alkyl, -phenyl-(R 10 ) x , or -COO-Ci-C 4 -alkyl;
  • R 9 is H, Ci-Cs-alkyl, -phenyl-(R 10 ) x , or -COO-Ci-C 4 -alkyl;
  • each R 10 is independently halo, Ci-C 4 -alkyl, -0-Ci-C6-alkyl, or -S-Ci-C 4 -alkyl; and each x is independently 0, 1, or 2.
  • the present invention is a process comprising the step of dehydrating a compound of Formula (V):
  • R 2 is Ci-C 4 -alkyl.
  • Compounds of Formula (II) have shown promise as intermediates to compounds useful for treating bacterial infections.
  • the present invention is a process comprising dehydrating a compound of Formula (I):
  • R x -R 7 are as previously defined.
  • Ci-C4-alkyl is used herein to refer to a straight chain or branched alkyl group with up to four carbon atoms. Examples include methyl, ethyl, w-propyl, isopropyl, w-butyl, sec-butyl, and ?-butyl.
  • Ci-C3-alkyl refers to methyl, ethyl, w-propyl, or isopropyl.
  • R 4 , R 5 , and R 6 are each independently H or Ci-C4-alkyl.
  • R 4 , R 5 , and R 6 are each independently H or methyl.
  • each of R 4 , R 5 , and R 6 is H.
  • dehydrating reagents examples include trifluoromethanesulfonic anhydride (Tf 2 0) and phosphorus pentoxide (P2O5), preferably Tf 2 0.
  • the reaction of Compound (I) to Compound (II) [or Compound (V) to Compound (VI)] is advantageously carried out in the presence of a suitable base, preferably an organic base such as pyridine, triethylamine, or diisopropylethylamine.
  • a suitable base preferably an organic base such as pyridine, triethylamine, or diisopropylethylamine.
  • the base is used in a range of from 1 equivalent with respect to Compound (I) to less than the amount, in equivalents, of the dehydrating reagent.
  • the compound of Formula (4) can be prepared by deprotecting a compound of Formula (3):
  • a strong acid such as HC1, H 2 S0 4 , MsOH or TsOH.
  • the compound of Formula (3) can be prepared by condensing a compound of Formula (1):
  • condensation conditions for example, in the presence of 1, 1'- carbonyldiimidazole.
  • Suitable reducing reagents include diisobutylaluminium hydride, LiAlH 4 , LiBH 4 , and NaBH 4 .
  • the compound of Formula (III) can be contacted with a suitable oxidizing reag to form a compound of Formula (IV):
  • Suitable oxidizing reagents include M11O 2 , Swern oxidation reagents, 2-iodoxybenzoic acid, pyridine sulphur trioxide, and Dess-Martin periodinane.
  • Scheme 1 illustrates one aspect of the present invention.
  • Compound (3) can be prepared by contacting acid (1) with alcohol (2) under suitable condensation conditions, for example, in the presence of 1 , 1 '-carbonyldiimidazole.
  • the protecting group is removed from compound (3) to form amine (4) under suitable deprotecting conditions, preferably by reaction with a strong acid, such as HC1, H2SO4, MsOH or TsOH.
  • the compound of Formula (Ila) can be prepared by treatment of the compound of Formula (la) with suitable base and dehydrating reagent, for example, pyridine and Tf 2 0.
  • suitable base and dehydrating reagent for example, pyridine and Tf 2 0.
  • the compound of Formula (IVa) can be prepared in at least two ways.
  • the compound of Formula (Ila) can be reduced to alcohol (Ilia) using a suitable reducing reagent such as diisobutylaluminium hydride, LiAlH 4 , LiBH 4 , or NaBH 4 .
  • Alcohol (Ilia) can then be oxidized to form the compound of Formula (IVa) using a suitable oxidizing reagent such as Mn0 2 , Swern oxidation reagents, 2-iodoxybenzoic acid, pyridine sulphur trioxide, or Dess-Martin periodinane.
  • a suitable oxidizing reagent such as Mn0 2 , Swern oxidation reagents, 2-iodoxybenzoic acid, pyridine sulphur trioxide, or Dess-Martin periodinane.
  • the compound of Formula (Ila) can be reduced to form the compound of Formula (IVa) using a suitable reducing reagent such as diisobutylaluminium hydride.
  • Scheme 2 Another embodiment of the present invention is illustrated in Scheme 2.
  • the compound of Formula (IVb) can be prepared in a similar manner as the compounds in Scheme 1 starting from alcohol (6).
  • Methanesulfonic acid 34 g, 1.25 eq
  • the mixture was stirred at 40 °C for 2 h then cooled to 20 °C.
  • the mixture was then transferred into a vessel containing dimethyl oxalate (34 g, 1 eq) and the temperature of the vessel was maintained at 20 °C with stirring.
  • Triethylamine 43 g, 1.5 eq was then added to this mixture stirring was continued for a further 1 h.
  • the mixture was washed with water (125 mL).
  • the aqueous layer was extracted with DCM (85 mL).
  • the combined organic layers were washed first with water (127.5 mL) and 10 wt% citric acid solution (170 mL).
  • 6N HC1 (127.5 mL) was added to the mixture to form a biphasic mixture.
  • the two layers were separated and the organic layer was extracted with 6 N HC1 (85 mL).
  • the acidic aqueous layers were combined and DCM (127.5 mL) was added. While maintaining the temperature below 25 °C, 28 wt% aqueous NH 4 OH was slowly added until the pH of the aqueous layer reached 3-5.
  • the two layers were separated and the aqueous layer was extracted with DCM (85 mL).
  • Pent-4-en- 1 -yl 2-(2-ethoxy-2-oxoacetamido)propanoate (1.05 g, 1 eq) and DCM (15 mL) were added to a vessel with stirring. Pyridine (0.39 g, 1.2 eq) was then added and the mixture was cooled to 15 °C. Tf 2 0 (1.7 g, 1.5 eq) was added to the mixture over 15 min and the mixture was warmed to ambient temperature to stir for 1.5 h. The reaction was quenched by the addition of DCM and 20 wt% aqueous NaOAc to form a biphasic mixture. The layers were separated and the organic layer was washed with water.
  • Pent-4-en- 1 -yl 2-(2-ethoxy-2-oxoacetamido)-3-phenylpropanoate was prepared in a similar manner as Example 2(a) starting with N-(?-butoxycarbony ⁇ phenylalanine (1.0 g).
  • the mixture was washed with 20 wt% aqueous NaOAc (2 x 1.5 mL), 10 wt% aqueous citric acid (3 x 1.5 mL), and water (1 x 1.5 mL). The organic layer was then concentrated under reduced pressure to provide the title compound as a solid.
  • Ethyl-2-((2-(hex-5-en-l-yloxy)-2-oxoethyl)amino)-2-oxoacetate (0.35 g) and DCM (4 mL) were added to a vessel with stirring followed by the addition of pyridine (0.13 g). Tf 2 0 (0.58 g) was then added to the mixture slowly at ambient temperature. The mixture was stirred at ambient temperature for 4 days after which time the mixture was extracted with 6N HC1 (3 x 10 mL). The combined acid layers were washed with DCM (10 mL) and the pH was adjusted to -10 with solid K2CO 3 . The basic aqueous layer was extracted with DCM (20 mL).
  • the mixture was stirred at ⁇ 0 to 7 °C for ⁇ 5 to 8 h then quenched with aqueous 5 wt% NaHCC solution (3 L) to form a biphasic mixture.
  • the layers were separated and the aqueous layer was extracted with DCM (0.9 L).
  • the combined organic layers were washed with aqueous 5 wt% citric acid (3.0 L) and brine (300 mL), dried over anhydrous sodium sulfate and filtered to provide the title compound in DCM solution.

Abstract

The present invention relates to a process comprising the step of dehydrating a compound of Formula (I): with a suitable dehydrating reagent to form a compound of Formula (II): wherein R1-R7 as defined herein. Compounds of Formula (II) have shown promise as intermediates to compounds useful for treating bacterial infections.

Description

PROCESS FOR PREPARING PYRANO-[2,3-c] PYRIDINE DERIVATIVES BACKGROUND OF THE INVENTION
The present invention relates to pyrano-[2,3-c]pyridine derivatives and methods for their preparation. 3,4-Dihydro-2H-pyrano[2,3-c]pyridine-6-carbaldehyde, disclosed in WO2004058144, is characterized by the following Formula (VIII):
Figure imgf000003_0001
(VIII)
Pyrano-[2,3-c]pyridine derivatives have shown promise as useful intermediates to compounds useful for treating bacterial infections. Previously disclosed methods for preparing pyrano-[2,3-c]pyridine-6-carbaldehyde are arduous, requiring many steps using expensive starting materials and resulting in unsatisfactory overall yields. (See
WO2003042210, Example 18; WO2004058144, Example 126(a)-(e)) It would therefore be advantageous to discover alternative ways of preparing this building block from relatively inexpensive chemicals.
SUMMARY OF THE INVENTION
In one aspect, the present invention is a process comprising dehydrating a compound of Formula (I):
Figure imgf000003_0002
(I)
with a suitable dehydrating reagent t form a compound of Formula (II):
Figure imgf000003_0003
(II) wherein R1 is -CH=CH-R8 or -CH2-CH=CH-R9;
R2 is Ci-C4-alkyl;
R3 is H, Ci-C4-alkyl, benzyl, -phenyl-(R10)x, or -Ci-C4-alkyl-COO-Ci-C4-alkyl;
each R4 is independently H, or Ci-C4-alkyl;
each R5 and each R6 are independently H, Ci-C4-alkyl, -0-Ci-C4-alkyl, or -S-Ci-C4-alkyl; R7 is R8 or -CH2-R9;
R8 is H, Ci-C4-alkyl, -phenyl-(R10)x, or -COO-Ci-C4-alkyl;
R9 is H, Ci-Cs-alkyl, -phenyl-(R10)x, or -COO-Ci-C4-alkyl;
each R10 is independently halo, Ci-C4-alkyl, -0-Ci-C6-alkyl, or -S-Ci-C4-alkyl; and each x is independently 0, 1, or 2.
In another aspect, the present invention is a process comprising the step of dehydrating a compound of Formula (V):
Figure imgf000004_0001
(V)
with a suitable dehydrating reagent to form a compound of Formula (VI):
Figure imgf000004_0002
(VI)
wherein R2 is Ci-C4-alkyl. Compounds of Formula (II) have shown promise as intermediates to compounds useful for treating bacterial infections.
DETAILED DESCRIPTION OF THE INVENTION
In a first aspect, the present invention is a process comprising dehydrating a compound of Formula (I):
Figure imgf000004_0003
(I) with a suitable dehydrating reagent to form a com ound of Formula (II):
Figure imgf000005_0001
wherein Rx-R7 are as previously defined.
Ci-C4-alkyl is used herein to refer to a straight chain or branched alkyl group with up to four carbon atoms. Examples include methyl, ethyl, w-propyl, isopropyl, w-butyl, sec-butyl, and ?-butyl.
Similarly, Ci-C3-alkyl refers to methyl, ethyl, w-propyl, or isopropyl.
In another embodiment, R4, R5, and R6 are each independently H or Ci-C4-alkyl.
In another embodiment, R4, R5, and R6 are each independently H or methyl.
In another embodiment, each of R4, R5, and R6 is H.
Examples of suitable dehydrating reagents include trifluoromethanesulfonic anhydride (Tf20) and phosphorus pentoxide (P2O5), preferably Tf20.
The reaction of Compound (I) to Compound (II) [or Compound (V) to Compound (VI)] is advantageously carried out in the presence of a suitable base, preferably an organic base such as pyridine, triethylamine, or diisopropylethylamine. Preferably, the base is used in a range of from 1 equivalent with respect to Compound (I) to less than the amount, in equivalents, of the dehydrating reagent.
A compound of Formula la):
Figure imgf000005_0002
(la)
be prepared, for example, by reaction of CI-CO-CO2-R2 with a compound of Formula
(4):
Figure imgf000005_0003
(4) in the presence of a suitable base, preferably an organic base, where R8 is as previously defined.
The compound of Formula (4) can be prepared by deprotecting a compound of Formula (3):
BocHN
Figure imgf000006_0001
under suitable deprotecting conditions, preferably by reaction with a strong acid, such as HC1, H2S04, MsOH or TsOH.
The compound of Formula (3) can be prepared by condensing a compound of Formula (1):
BocHN
Figure imgf000006_0002
with a compound of Formula (2):
Figure imgf000006_0003
under suitable condensation conditions, for example, in the presence of 1, 1'- carbonyldiimidazole.
A compound of Formula lb):
Figure imgf000006_0004
can be prepared in a similar manner to the compound of Formula (la), where R9 is as previously defined. compound of Formula II)
Figure imgf000007_0001
(II)
be contacted with a suitable reducin reagent to form a compound of Formula (III)
Figure imgf000007_0002
(HI)
Examples of suitable reducing reagents include diisobutylaluminium hydride, LiAlH4, LiBH4, and NaBH4.
The compound of Formula (III) can be contacted with a suitable oxidizing reag to form a compound of Formula (IV):
Figure imgf000007_0003
(IV)
Examples of suitable oxidizing reagents include M11O2, Swern oxidation reagents, 2-iodoxybenzoic acid, pyridine sulphur trioxide, and Dess-Martin periodinane.
Alternatively, the compound of Form la (IV):
Figure imgf000007_0004
(IV) can be prepared by reducing the com ound of Formula (II):
Figure imgf000008_0001
(II)
a suitable reducing reagent, such as diisobutylaluminium hydride. Schemes
Scheme 1 illustrates one aspect of the present invention. Compound (3) can be prepared by contacting acid (1) with alcohol (2) under suitable condensation conditions, for example, in the presence of 1 , 1 '-carbonyldiimidazole. The protecting group is removed from compound (3) to form amine (4) under suitable deprotecting conditions, preferably by reaction with a strong acid, such as HC1, H2SO4, MsOH or TsOH.
The compound of Formula (la) can be prepared by contacting amine (4) with X- CO-CO2- 2 (X= halo or -OCH3) in the presence of a suitable base, preferably, an organic base such as triethylamine.
The compound of Formula (Ila) can be prepared by treatment of the compound of Formula (la) with suitable base and dehydrating reagent, for example, pyridine and Tf20.
The compound of Formula (IVa) can be prepared in at least two ways. For example, the compound of Formula (Ila) can be reduced to alcohol (Ilia) using a suitable reducing reagent such as diisobutylaluminium hydride, LiAlH4, LiBH4, or NaBH4.
Alcohol (Ilia) can then be oxidized to form the compound of Formula (IVa) using a suitable oxidizing reagent such as Mn02, Swern oxidation reagents, 2-iodoxybenzoic acid, pyridine sulphur trioxide, or Dess-Martin periodinane.
Alternatively, the compound of Formula (Ila) can be reduced to form the compound of Formula (IVa) using a suitable reducing reagent such as diisobutylaluminium hydride.
Figure imgf000009_0001
Another embodiment of the present invention is illustrated in Scheme 2. The compound of Formula (IVb) can be prepared in a similar manner as the compounds in Scheme 1 starting from alcohol (6).
Figure imgf000010_0001
EXAMPLES
The following examples are illustrative of the process of the present invention and are not intended to limit the scope of the invention. Example 1; Methyl 3,4-dihydro-2H-pyrano[2,3-c]pyridine-6-carboxylate
Figure imgf000011_0001
(a) Methyl 2-oxo-2-((2-oxo-2-(pent-4-en- 1 -yloxy)ethyl)amino)acetate
Figure imgf000011_0002
To a 1-L reactor was charged Ι, Γ-carbonyldiimidazole (CDI) (44.0 g, 0.95 eq) and tert-butyl methyl ether (TBME) (150 mL). The mixture was heated with stirring to ~ 40 °C whereupon a solution of N-Boc-glycine (50 g, 1 eq) in TBME (200 mL) was added and stirring continued for 0.5 h. Pent-4-en- 1 -ol (23 g, 0.95 eq) was then added over 30 min and stirring was continued at 40 °C for 2 h then cooled to 20 °C. IN HCl (125 mL) was added to form a biphasic mixture. The layers were separated and the organic layer was washed with IN HCl (1 x 125 mL) followed by water (1 x 125 mL). The TBME was distilled off and the crude pent-4-en-l-yl 2-((tert-butoxycarbonyl)amino)acetate was then
azeotropically dried with toluene (200 mL). The mixture was heated to 40 °C and sufficient toluene was added to bring the total volume of toluene to -200 mL.
Methanesulfonic acid (34 g, 1.25 eq) was added and the mixture was stirred at 40 °C for 2 h then cooled to 20 °C. The mixture was then transferred into a vessel containing dimethyl oxalate (34 g, 1 eq) and the temperature of the vessel was maintained at 20 °C with stirring. Triethylamine (43 g, 1.5 eq) was then added to this mixture stirring was continued for a further 1 h. The mixture was washed with water (125 mL). The toluene solution was concentrated with azeotropic drying to give methyl 2-oxo-2-((2-oxo-2-(pent- 4-en-l-yloxy)ethyl)amino)acetate as an oil. XH NMR (400 MHz, CDCh) δ ppm 7.55 (s, 1 H), 5.73-5.86 (m, 1 H), 4.97-5.10 (m, 2 H), 4.21 (t, J=6.65 Hz, 2 H), 4.13 (d, J=5.52 Hz, 2 H), 3.93 (s, 3 H), 2.13 (q, J=7.42 Hz, 2 H), 1.71-1.85 (m, 2 H); 13C MR (75 MHz, CDCh) δ ppm 168.58, 160.35, 156.29, 137.05, 1 15.56, 65.25, 53.72, 41.48, 29.84, 27.56; HRMS (M+Na) m/z, calcd for Ci0H15NO5Na, 252.0848; found, 252.0852. (b) The Title Compound
Methyl 2-oxo-2-((2-oxo-2-(pent-4-en-l-yloxy)ethyl)amino)acetate (42.5 g, 1 eq) and dichloromethane (DCM) (425 mL) were added to a vessel with stirring followed by the addition of pyridine (17.6 g, 1.2 eq). Tf20 (78.5 g, 1.5 eq) was added over 45 min to the mixture maintaining an internal temperature of ~25 °C. The mixture was stirred for 6 h at which point the reaction was carefully quenched by the addition of 20 wt% aqueous NaOAc (255 mL) to form a biphasic solution. The aqueous layer was extracted with DCM (85 mL). The combined organic layers were washed first with water (127.5 mL) and 10 wt% citric acid solution (170 mL). 6N HC1 (127.5 mL) was added to the mixture to form a biphasic mixture. The two layers were separated and the organic layer was extracted with 6 N HC1 (85 mL). The acidic aqueous layers were combined and DCM (127.5 mL) was added. While maintaining the temperature below 25 °C, 28 wt% aqueous NH4OH was slowly added until the pH of the aqueous layer reached 3-5. The two layers were separated and the aqueous layer was extracted with DCM (85 mL). The combined organic layers were washed with water (85 mL). The organic solution was concentrated under reduced pressure to provide the title compound as an oil which solidified on standing. XH NMR (400 MHz, CDCI3) ½pm 8.17 (s, 1 H), 7.80-7.86 (m, 1 H), 4.26 (t, J=5.19 Hz, 2 H), 3.92 (s, 3 H), 2.79 (t, J=6.44 Hz, 2 H), 1.97-2.09 (m, 2 H); 13C NMR (75 MHz, CDCI3) δ ppm 165.1 1, 154.25, 138.95, 138.64, 130.06, 126.13, 65.55, 51.99, 23.57, 20.67; HRMS (M+Na) m/z, calcd for CioHuN03Na, 216.0637; found, 216.0643.
Example 2; Ethyl 8-methyl-3,4-dihydro-2H-pyrano [2,3-c] pyridine-6-carboxylate
Figure imgf000012_0001
(a) Pent-4-en- 1 -yl 2-(2-ethoxy-2-oxoacetamido)propanoate
Figure imgf000012_0002
N-(?-Butoxycarbonyl)alanine (3.1 g, 1 eq) and DCM (50 mL) were added to a vessel with stirring followed by the addition of CDI (3.1 g, 1.15 eq). The mixture was stirred at ambient temperature for 18 h after which time 4-penten- 1 -ol (1.8 g, 1.25 eq) was added. The mixture was stirred a further 18 h at ambient temperature at which point the reaction was quenched with IN HC1. A biphasic mixture was formed and the layers were separated. The organic layer was washed with saturated aqueous NaHCCh solution and then concentrated to give pent-4-en-l-yl 2-((tert-butoxycarbonyl)amino)propanoate as an oil. The oil was dissolved in DCM (50 mL) and methanesulfonic acid (2.2 g, 1.4 eq) was added. The mixture was stirred at ambient temperature for ~22 h then cooled in an ice/water bath. Ethyl 2-chloro-2-oxoacetate (3.4 g, 1.5 eq) was added followed by drop- wise addition of triethylamine (5.0 g, 3 eq). The mixture was stirred for 7 h after which time the reaction was quenched by IN HC1 to form a biphasic mixture. The layers were separated and the organic layer was washed with a saturated aqueous NaHC03 solution. The organic layer was then concentrated under reduced pressure to provide pent-4-en- 1 -yl 2-(2-ethoxy-2-oxoacetamido)propanoate as a yellow oil. XH NMR (400 MHz, CDC ) ½pm 7.64 (d, J=6.94 Hz, 1 H), 5.66-5.83 (m, 1 H), 4.90-5.05 (m, 2 H), 4.49-4.62 (m, 1 H), 4.31 (qd, J=7.17, 2.26 Hz, 2 H), 4.13 (td, J=6.59, 2.13 Hz, 2 H), 2.02-2.14 (m, 2 H), 1.67-1.78 (m, 2 H), 1.44 (d, J=7.19 Hz, 3 H), 1.34 (t, J=7.15 Hz, 3 H); 13C NMR (75 MHz, CDCh) δ ppm 171.64, 159.94, 155.83, 136.94, 1 15.40, 64.98, 63.10, 48.40, 29.71, 27.44, 17.88, 13.80; HRMS (M+Na) m/z, calcd for Ci2H19N05Na, 280.1 161; found, 280.1166.
(b) The Title Compound
Pent-4-en- 1 -yl 2-(2-ethoxy-2-oxoacetamido)propanoate (1.05 g, 1 eq) and DCM (15 mL) were added to a vessel with stirring. Pyridine (0.39 g, 1.2 eq) was then added and the mixture was cooled to 15 °C. Tf20 (1.7 g, 1.5 eq) was added to the mixture over 15 min and the mixture was warmed to ambient temperature to stir for 1.5 h. The reaction was quenched by the addition of DCM and 20 wt% aqueous NaOAc to form a biphasic mixture. The layers were separated and the organic layer was washed with water. The organic layer was then concentrated under reduced pressure to provide the title compound as yellow solid. XH NMR (300 MHz, CDCh) δ ppm 7.62 (s, 1 H), 4.32 (q, J=7.12 Hz, 2 H), 4.16- 4.25 (m, 2 H), 2.70 (t, J=6.44 Hz, 2 H), 2.37 (s, 3 H), 1.86 - 2.03 (m, 2 H), 1.31 (t, J=7.12 Hz, 3 H); 13C NMR (75 MHz, CDCh) 5 ppm 165.15, 152.44, 147.98, 137.72, 128.73, 124.80, 66.85, 61.09, 23.98, 21.06, 18.98, 14.11 ; HRMS (M+H) m/z, calcd for Ci2H16N03, 222.1 130; found, 222.1133. Example 3; Ethyl 8-benzyl-3,4-dihydro-2H-pyrano [2,3-c]pyridine-6-carboxylate
Figure imgf000014_0001
(a) Pent-4-en-l-yl 2-(2-ethoxy-2-oxoacetamido)-3-phenylpropanoate
Figure imgf000014_0002
Pent-4-en- 1 -yl 2-(2-ethoxy-2-oxoacetamido)-3-phenylpropanoate was prepared in a similar manner as Example 2(a) starting with N-(?-butoxycarbony ^phenylalanine (1.0 g). 'H NMR (400 MHz, CDCk) ½pm 7.52 (d, J=8.03 Hz, 1 H), 7.28-7.37 (m, 3 H), 7.15-7.19 (m, 2 H), 5.73-5.84 (m, 1 H), 5.06-5.10 (m, 1 H), 5.01-5.05 (m, 1 H), 4.87-4.95 (m, 1 H), 4.38 (qd, J=7.15, 1.72 Hz, 2 H), 4.11-4.21 (m, 2 H), 3.21 (d, J=6.1 1 Hz, 2 H), 2.05-2.13 (m, 2 H), 1.69-1.79 (m, 2 H), 1.41 (t, J=7.15 Hz, 3 H); 13C NMR (75 MHz, CDCk) δ ppm 170.30, 159.85, 155.93, 137.01, 135.14, 129.10, 128.62, 127.26, 1 15.43, 65.10, 63.22, 53.57, 37.70, 29.75, 27.42, 13.85; HRMS (M+H) m/z, calcd for
Figure imgf000014_0003
334.1654; found 334.1665.
(b) The Title Compound Pent-4-en-l-yl 2-(2-ethoxy-2-oxoacetamido)-3-phenylpropanoate (0.80 g, 1 eq) and
DCM (15 mL) were added to a vessel with stirring. Pyridine (0.23 g, 1.2 eq) was then added and the mixture was cooled to 15 °C. Tf20 (1.0 g, 1.5 eq) was added to the mixture over 15 min and the mixture was warmed to ambient temperature. The solution was stirred for 3.5 h after which time the reaction was quenched by DCM and 20 wt% aqueous NaOAc to form a biphasic mixture. The layers were separated and the organic layer was extracted with 6N HC1 (3 x 10 mL). The combined acid layers were washed with DCM and the pH was adjusted to ~9 with solid K2CO3. The basic aqueous layer was extracted with DCM. The organic layer was concentrated under reduced pressure to provide the title compound. ¾ NMR (300 MHz, CDC ) δ ppm 7.74 (s, 1 H), 7.10-7.35 (m, 5 H), 4.43 (q, J=7.12 Hz, 2 H), 4.22-4.29 (m, 2 H), 4.21 (s, 2 H), 2.78 (t, J=6.41 Hz, 2 H), 1.93-2.06 (m, 2 H), 1.41 (t, J=7.12 Hz, 3 H); 13C MR (75 MHz, CDCh) δ ppm 165.08, 152.25, 149.62, 138.86, 138.06, 129.62, 128.61, 127.80, 125.61, 125.23, 66.70, 60.97, 38.55, 23.93, 20.92, 14.10; HRMS (M+H) m/z, calcd for Ci8H2oN03, 298.1443; found 298.1450.
Example 4; Ethyl 8-phenyl-3,4-dihydro-2H-pyrano [2,3-c]pyridine-6-carboxylate
Figure imgf000015_0001
(a) Ethyl 2-oxo-2-((2-oxo-2-(pent-4-en- 1 -yloxy)- 1 -phenylethyl)amino)acetate
Figure imgf000015_0002
Ethyl 2-oxo-2-((2-oxo-2-(pent-4-en-l -yloxy)- l-phenylethyl)amino)acetate was prepared in a similar manner as Example 2(a) starting from -[[(l,l- dimethylethoxy)carbonyl] amino] -benzeneacetic acid (0.96 g). XH NMR (400 MHz, CDCh) δ ppm 8.01 (d, J=7.11 Hz, 1 H), 7.32-7.43 (m, 5 H), 5.63-5.78 (m, 1 H), 5.58 (d, J=7.61 Hz, 1 H), 4.88-4.98 (m, 2 H), 4.36 (q, J=7.11 Hz, 2 H), 4.11-4.24 (m, 2 H), 1.93- 2.04 (m, 2 H), 1.70 (qd, J=7.12, 6.88, 2.05 Hz, 2 H), 1.39 (t, J=7.15 Hz, 3 H); 13C MR (75MHz, CDCh) δ ppm 169.75, 159.93, 155.72, 136.94, 135.47, 129.02, 128.83, 127.26, 115.53, 65.40, 63.32, 56.69, 29.63, 27.44, 13.91; HRMS (M+H) m/z, calcd for Ci7H22N05, 320.1498; found 320.1512.
(b) The Title Compound Ethyl 8-phenyl-3,4-dihydro-2H-pyrano[2,3-c]pyridine-6-carboxylate was prepared in a similar manner as Example 3(b) starting from ethyl 2-oxo-2-((2-oxo-2-(pent-4-en-l- yloxy)-l-phenylethyl)amino)acetate (0.91 g). lR NMR (300 MHz, CDCh) δ ppm 7.91- 7.98 (m, 2 H), 7.84 (s, 1 H), 7.34-7.49 (m, 3 H), 4.44 (q, J=7.12 Hz, 2 H), 4.29-4.38 (m, 2 H), 2.91 (t, J=6.44 Hz, 2 H), 2.02-2.18 (m, 2 H), 1.43 (t, J=7.12 Hz, 3 H); 13C NMR (75 MHz, CDCli) ½ m 165.1 1, 152.06, 149.30, 146.60, 138.65, 136.72, 135.82, 130.64, 129.30, 128.06, 127.59, 125.48, 66.89, 61.07, 24.37, 20.84, 14.09; HRMS (M+H) m/z, calcd for Ci7H18N03, 284.1287; found 284.1301.
Example 5; Methyl 5-methyl-3,4-dihydro-2H-pyrano [2,3-c] pyridine-6-carboxylate
Figure imgf000016_0001
(a) (is)-Methyl 2-((2-(hex-4-en-l-yloxy)-2-oxoethyl)amino)-2-oxoacetate
Figure imgf000016_0002
To a vessel maintained at 40 °C was charged CDI (2.75 g, 0.95 eq) and TBME (9 mL). To this mixture was added with stirring a solution of N-(?-butoxycarbonyl)glycine (3.1 g, 1.0 eq) dissolved in TBME (12 mL) over 30 min. Stirring was continued for an additional 30 min, whereupon trans-4-hexen-l-ol (1.7 g, 0.95 eq) was added over 30 min. The mixture was maintained with stirring at 40 °C for an additional 3.5 h, then cooled to ambient temperature and stirred a further 14 h. The mixture was washed with IN HQ (2 x 7.8 mL) then water (1 x 7.8 mL). The organic layer was dried over a2S04, filtered and concentrated to give (£)-hex-4-en-l-yl 2-((tert-butoxycarbonyl)amino)acetate as an oil. The oil was dissolved in DCM (12 mL) and 4.0 M HC1 in dioxane (2.8 mL) was added drop-wise. The mixture was stirred at ambient temperature for 1.5 h then the mixture was heated to 35 °C and stirred for 3 h. 4.0 M HC1 in dioxane (2.8 mL) was added drop-wise. After 6 h at 35 °C a further dose of 4.0 M HC1 in dioxane (2.8 mL) was added drop-wise and the mixture was stirred for a further 4 h. The mixture was cooled to ambient temperature and the solvent was removed under reduced pressure. A portion of the residue (1.0 g) was dissolved in DCM (8 mL) and methyl 2-chloro-2-oxoacetate (0.63 g) was added. Triethylamine (1.0 g) was added drop-wise over 20 min. The mixture was stirred for 1 h before being quenched by IN HC1 (2.5 mL) to form a biphasic mixture. The layers were separated and the organic layer was washed with IN HCl (1 x 2.5 mL), water (1 x 2.5 mL) and concentrated under reduced pressure to provide an oil. Flash column
chromatography (S1O2, 10->60% EtO Ac/Hex gradient) provided the title compound as an oil as a 95:5 mixture of trans:cis isomers. XH NMR (300 MHz, CDCI3) δ ppm 7.57 (s, 1 H), 5.31-5.55 (m, 2 H), 4.17 (t, J=6.69 Hz, 2 H), 4.12 (d, J=5.51 Hz, 2 H), 3.92 (s, 3 H), 1.97-2.10 (m, 2 H), 1.67-1.77 (m, 2 H), 1.62-1.67 (m, 3 H); 13C NMR (75 MHz, CDCI3) δ ppm 168.60, 160.35, 156.28, 129.49, 126.12, 65.34, 53.68, 41.47, 28.62, 28.17, 17.84; HRMS (M+H) m/z, calcd for CnH18N05, 244.1185; found 244.1 187.
(b) The Title Compound (Zs)-Methyl 2-((2-(hex-4-en-l-yloxy)-2-oxoethyl)amino)-2-oxoacetate (0.24 g, 1 eq) and DCM (2.4 mL) were added to a vessel with stirring followed by the addition of pyridine (95 mg, 1.2 eq). Tf20 (0.42 g, 1.5 eq) was then added over 45 min at ambient temperature and the mixture was stirred at ambient temperature for 48 h. The mixture was washed with 20 wt% aqueous NaOAc (2 x 1.5 mL), 10 wt% aqueous citric acid (3 x 1.5 mL), and water (1 x 1.5 mL). The organic layer was then concentrated under reduced pressure to provide the title compound as a solid. XH NMR (300 MHz, CDC13) δ ppm 8.10 (s, 1 H), 4.15-4.25 (m, 2 H), 3.94 (s, 3 H), 2.71 (t, J=6.56 Hz, 2 H), 2.47 (s, 3 H), 2.00-2.18 (m, 2 H); 13C NMR (75 MHz, CDCI3) δ ppm 166.71, 153.50, 138.69, 136.72, 135.67, 130.36, 65.93, 52.35, 22.18, 21.49, 14.57; HRMS (M+H) m/z, calcd for CnH14N03, 208.0974; found 208.0981.
Example 6; Ethyl 5-methyl-3,4-dihydro-2H-pyrano [2,3-c] pyridine-6-carboxylate
Figure imgf000017_0001
(a) Ethyl 2-((2-(hex-5-en-l-yloxy)-2-oxoethyl)amino)-2-oxoacetate
Figure imgf000017_0002
Ethyl 2-((2-(hex-5-en-l-yloxy)-2-oxoethyl)amino)-2-oxoacetate was prepared in a similar manner as Example 2(a) starting from N-(/-butoxycarbonyl)glycine (2.8 g) and 5- hexen-l-ol (2.08 g). XH NMR (300 MHz, CDC ) δ ppm 7.60 (s, 1 H), 5.66-5.86 (m, 1 H), 4.88-5.06 (m, 2 H), 4.35 (q, J=7.12 Hz, 2 H), 4.17 (t, J=6.63 Hz, 2 H), 4.11 (d, J=5.57 Hz,
2 H), 2.06 (q, J=7.16 Hz, 2 H), 1.59-1.72 (m, 2 H), 1.39-1.51 (m, 2 H), 1.37 (t, J=7.15 Hz,
3 H); 13C MR (75 MHz, CDCh) δ ppm 168.67, 159.84, 156.57, 138.00, 1 14.93, 65.66, 63.25, 41.41, 33.07, 27.77, 24.91, 13.88; HRMS (M+H) m/z, calcd for Ci2H20NO5,
258.1341; found 258.1349.
(b) The Title Compound (A)
Figure imgf000018_0001
3 : 1
Ethyl-2-((2-(hex-5-en-l-yloxy)-2-oxoethyl)amino)-2-oxoacetate (0.35 g) and DCM (4 mL) were added to a vessel with stirring followed by the addition of pyridine (0.13 g). Tf20 (0.58 g) was then added to the mixture slowly at ambient temperature. The mixture was stirred at ambient temperature for 4 days after which time the mixture was extracted with 6N HC1 (3 x 10 mL). The combined acid layers were washed with DCM (10 mL) and the pH was adjusted to -10 with solid K2CO3. The basic aqueous layer was extracted with DCM (20 mL). The organic layer was concentrated under reduced pressure to provide the title compound (A) and ethyl 2,3,4,5-tetrahydrooxepino[2,3-c]pyridine-7-carboxylate (B) as a 3 : 1 mixture as based on NMR analysis. XH NMR (300 MHz, CDCh) δ ppm 8.38 (s, 0.3 H, cmpd B), 8.11 (s, 1 H, cmpd A), 7.95 (s, 0.3 H, cmpd B), 4.36-4.51 (m, 2.6 H, cmpd A/B CH3CH2), 4.17-4.25 (m, 2 Η, cmpd A OCH2), 4.06-4.13 (m, 0.6 Η, cmpd B OCH2), 2.85-2.93 (m, 0.6 Η, cmpd B CH2), 2.71 (t, J=6.53 Hz, 2 H, cmpd A CH2), 2.45 (s, 3 H, cmpd A CH3), 1.99-2.15 (m, 2.6 H, cmpd A/B CH2), 1.54-1.88 (m, 0.6 H, cmpd B CH2), 1.44 (t, J=7.12 Hz, 0.9 H, cmpd B CH3), 1.44 (t, J=7.12 Hz, 3 H, cmpd A CH3); 13C NMR (75 MHz, CDCh) δ ppm 166.53, 165.01, 162.88, 159.21, 153.21, 143.48, 143.1 1, 142.72, 139.52, 136.74, 134.94, 130.12, 127.21, 73.82, 65.85, 61.61, 61.21, 33.74, 31.53, 24.97, 22.1 1, 21.48, 14.56, 14.28; Cmpd A: HRMS (M+Na) m/z, calcd for Ci2H15N03Na, 244.0950; found 244.0961; Cmpd B: HRMS (M+H) m/z, calcd for Ci2H16N03, 222.1 130; found 222.1 130. Example 7; 3,4-Dihydro-2H-pyrano [2,3-c] pyridine-6-carbaldehyde
Figure imgf000019_0001
(VIII)
(a) (3,4-Dihydro-2H-pyrano[2,3-c]pyridin-6-yl)methanol
Figure imgf000019_0002
(VII)
To a vessel was added with stirring methyl 3,4-dihydro-2H-pyrano[2,3-c]pyridine-6- carboxylate (7.4 g, 1 eq) and tetrahydrofuran (THF) (32 mL). The mixture was heated to 55 °C whereupon 2M LiBH4 in THF solution (20 mL, 1.05 eq.) was added over 1 h. The stirring continued at 55 °C until reduction was complete at which point the mixture was cooled to 45 °C and 6N HC1 (37 mL) was carefully added to the mixture. The stirring was continued for 1 h then the mixture was cooled to 25 °C. The pH was adjusted to -9.5 to 10 with 50 wt% aqueous NaOH solution. The organics were extracted with 2- methyltetrahydrofuran (2 x 37 mL). The combined organic layers were concentrated under reduced pressure and crystallized to provide (3,4-dihydro-2H-pyrano[2,3-c]pyridin-6- yl)methanol as an off-white solid. XH NMR (300 MHz, CDCk) δ ppm 8.10 (s, 1 H), 6.91- 6.99 (m, 1 H), 4.65 (s, 2 H), 4.18-4.29 (m, 2 H), 3.42 (s, 1 H), 2.79 (t, J=6.50 Hz, 2 H), 1.96-2.12 (m, 2 H); 13C NMR (75 MHz, CDCk) δ ppm 151.09, 150.39, 137.87, 131.40, 121.14, 66.51, 64.10, 24.22, 21.55; HRMS (M+H) m/z, calcd for C9H12N02, 166.0868; found, 166.0861.
(b) The Title Compound
(3,4-Dihydro-2H-pyrano[2,3-c]pyridin-6-yl)methanol (300 g, 1.0 eq), DCM (1.5 L) and dimethyl sulfoxide (216 mL, 2.05 eq) were added with stirring to a vessel maintained at ~0 to 5 °C. Triethylamine (858 mL, 4.1 eq) followed by solid pyridine sulphur trioxide (474 g, 2.0 eq) were slowly added to the mixture while maintaining the mixture temperature at ~0 to 7 °C. The mixture was stirred at ~0 to 7 °C for ~5 to 8 h then quenched with aqueous 5 wt% NaHCC solution (3 L) to form a biphasic mixture. The layers were separated and the aqueous layer was extracted with DCM (0.9 L). The combined organic layers were washed with aqueous 5 wt% citric acid (3.0 L) and brine (300 mL), dried over anhydrous sodium sulfate and filtered to provide the title compound in DCM solution. XH NMR (300 MHz, CDCk) δ ppm 9.94 (s, 1 H), 8.21-8.32 (m, 1 H), 7.72 (s, 1 H), 4.25-4.40 (m, 2 H), 2.85 (t, J=6.50 Hz, 2 H), 1.97-2.19 (m, 2 H).

Claims

What is claimed is:
1. A process comprising the ste of dehydrating a compound of Formula (I):
Figure imgf000021_0001
(I)
with a suitable dehydrating rea ent to form a compound of Formula (II):
Figure imgf000021_0002
(Π)
wherein R1 is -CH=CH-R8 or -CH2-CH=CH-R9;
R2 is Ci-C4-alkyl;
R3 is H, Ci-C4-alkyl, benzyl, -phenyl-(R10)x, or -Ci-C4-alkyl-COO-Ci-C4-alkyl; each R4 is independently H, or Ci-C4-alkyl;
each R5 and each R6 are independently H, Ci-C4-alkyl, -0-Ci-C4-alkyl, or -S-Ci-
C4-alkyl;
R7 is R8 or -CH2-R9;
R8 is H, Ci-C4-alkyl, -phenyl-(R10)x, or -COO-Ci-C4-alkyl;
R9 is H, Ci-C3-alkyl, -phenyl-(R10)x, or -COO-Ci-C4-alkyl;
each R10 is independently halo, Ci-C6-alkyl, -0-Ci-C4-alkyl, or -S-Ci-C4-alkyl; and each x is independently 0, 1, or 2.
The process of claim 1 which is further carried out in the presence of an organic base, wherein the dehydrating reagent is Tf20 or P2O5; and R4, R5, and R6 are each independently H or Ci-C4-alkyl.
The process of claim 2 wherein R4, R5, and R6 are each independently H or methyl; and the organic base is pyridine, triethylamine, or diisopropylethylamine.
The process claim 2 or 3 wherein each of R4, R5, and R6 is H; the dehydrating reagent is Tf20; and the organic base is used in an amount of at least 1 equivalent with respect to Compound (I) and less than the amount of the dehydrating reagent, in equivalents.
5. The process of claim 1, 2, 3, or 4 which further comprises the steps of:
a) reducing the compound of Formula (II) with a suitable reducing reagent to form a compound of Form la (III):
Figure imgf000022_0001
(III) ; and
b) oxidizing the compound of Formula (III) with a suitable oxidizing reagent to form a compound of Form la (IV):
Figure imgf000022_0002
(IV)
6. The process of claim 1, 2, 3, or 4 which further comprises the step of reducing the compound of Formula (II) with a suitable reducing reagent to form a compound of Formula (IV):
Figure imgf000022_0003
(IV)
7. A process comprising the step of dehydrating a compound of Formula (V):
Figure imgf000022_0004
(V) with a suitable dehydrating reagent to form a compound of Formula (VI):
Figure imgf000023_0001
(VI)
wherein R2 is Ci-C4-alkyl. 8. The process of claim 7 wherein the dehydrating reagent is Tf20 or P2O5.
9. The process of claim 7 or 8 wherein the dehydrating reagent is Tf20; and R2 is methyl or ethyl. 10. The process of claim 7, 8, or 9 wherein the process is carried out in the presence of an organic base in an amount of at least 1 equivalent with respect to Compound (V) and less than the amount of the dehydrating reagent, in equivalents.
11. The process of any of claims 7-10 which further comprises the steps of:
a) reducing the compound of Formula (VI) with a suitable reducing reagent to form a compound of Formula (VII):
Figure imgf000023_0002
WW ; and
b) oxidizing the compound of Formula (VII) with a suitable oxidizing reagent to form a compound of Formula (VIII):
Figure imgf000023_0003
(VIII)
12. The process of any of claims 7-10 which further comprises the step of reducing the compound of Formula (VI) with a suitable reducing reagent to form a compound of Formula (VIII):
Figure imgf000024_0001
(VIII)
13. The process of claim 5 or 11 wherein the reducing reagent is diisobutylaluminium hydride, LiAlH4, LiBH4, or NaBH4.
14. The process of claim 5, 11, or 13 wherein the reducing reagent is LiBH4.
15. The process of claim 5, 11, 13, or 14 wherein the oxidizing reagent is Mn02, Swern oxidation reagents, 2-iodoxybenzoic acid, pyridine sulphur trioxide, or Dess-Martin periodinane.
16. The process of claim 5, 1 1, 13, 14, or 15 wherein the oxidizing reagent is pyridine sulphur trioxide.
17. The process of claim 6 or 12 wherein the reducing reagent is diisobutylaluminium hydride.
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EP2595994A4 (en) 2014-12-10
EP2595994B1 (en) 2016-04-20
SG187146A1 (en) 2013-02-28
KR20130129902A (en) 2013-11-29
US20130116436A1 (en) 2013-05-09
CN103492393A (en) 2014-01-01
US8759523B2 (en) 2014-06-24
JP2013541498A (en) 2013-11-14
ES2574179T3 (en) 2016-06-15
EA201390016A1 (en) 2013-09-30
JP5762538B2 (en) 2015-08-12
EP2595994A2 (en) 2013-05-29
WO2012012391A3 (en) 2013-08-08

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