FI127376B

FI127376B - METHOD FOR THE MANUFACTURE OF BORAN COMPLEXES, REAGENTS APPLICABLE TO THE METHOD AND USE OF REAGENTS

Info

Publication number: FI127376B
Application number: FI20165285A
Authority: FI
Inventors: Kostiantyn Chernichenko; Timo Repo
Original assignee: Helsingin Yliopisto
Priority date: 2016-04-04
Filing date: 2016-04-04
Publication date: 2018-04-30
Also published as: WO2017174868A1; FI20165285A

Abstract

The present invention relates to a diborane-free method for producing borane complexes, such as borane dimethyl sulfide. The method includes reacting boron trifluoride and a Lewis base with a certain tertiary amines, such as 1,2,2,6,6- pentamethylpiperidineunder hydrogen atmosphere. The invention relates also to recovery of side products produced, and reagents for use in preparation of borane complexes.

Description

(54) Keksinnön nimitys - Uppfinningens benämning

MENETELMÄ BORAANIKOMPLEKSIEN VALMISTAMISEKSI, MENETELMÄÄN SOVELTUVAT REAGENSSIT SEKÄ REAGENSSIEN KÄYTTÖ

Förfarande för framställning av borankomplex, reagenser för förfarandet samt användning av reagenserna A METHOD TO PRODUCE BORANE COMPLEXES, REAGENTS FOR THE SAME, AND USE OF THE REAGENTS (56) Viitejulkaisut - Anförda publikationer

US 6248885 B1, WO 2009037306 A2, US 5212306 A, US 3103417 A (57) Tiivistelmä - Sammandrag

The present invention relates to a diborane-free method for producing borane complexes, such as borane dimethyl sulfide. The method includes reacting boron trifluoride and a Lewis base with a certain tertiary amines, such as 1,2,2,6,6-pentamethylpiperidine under hydrogen atmosphere. The invention relates also to recovery of side products produced, and reagents for use in preparation of borane complexes.

Keksintö koskee diboraanittoman menetelmän boraanikompeksien, kuten boraanidimetyylisulfidin valmistamiseksi. Menetelmä käsittää boraanitrifluoridin ja Lewisin mäksen reagoimisen tiettyjen tertiääristen amiinien kuten 1,2,2,6,6-pentametyylpiperidiinin kanssa vetyilmakehässä. Keksintö koskee myös sivutuotteiden palauttamisen, sekä reagenssit boraanikompleksien valmistamiseksi.

co io & ή m

! ί r

Γ^θ^3

-ISO -105 -110 -115 -120 -125 -138 -135 -148 -145 -ISO -155 -160 -165 -170 -175 ft foora)

20165285 prh 04-04-2016

A METHOD TO PRODUCE BORANE COMPLEXES, REAGENTS FOR THE SAME, AND USE OF THE REAGENTS

FIELD

The present invention relates to methods for producing of borane complexes, in particular to methods that do not involve use of diborane, sodium borohydride, or other flammable and/or toxic reagents. The invention relates also to reagents and their use in the method.

BACKGROUND

Borane complexes are widely used as hydrogen sources in chemical processes and io recently also in fuel cells. Borane complexes are typically produced by reacting diborane with the corresponding Lewis bases (L) acting as complexants. The general process is shown in equation (1):

B₂H₆ + 2 L —> 2 BHs- L (1)

The diborane used as a starting material, in turn, is prepared either by a two-stage process starting from boron trichloride or from inorganic borohydrides and tetrafluoroborates.

A widely used method for producing THF-borane includes treatment of sodium borohydride with iodine or sulfuric acid. Although the method is diborane free, it requires the use of sodium borohydride that is, in turn, prepared from a highly flammable sodium hydride.

Thus, there is a need for a method for the preparation of borane complexes that avoids the use of diborane and/or other toxic and flammable reagents such as alkali metal hydrides and borohydrides.

SUMMARY

In the present invention it was observed that borane complexes can be prepared by allowing boron trifluoride complexes, or boron trifluoride and a Lewis base, to react with certain sterically hindered amines and hydrogen. It was also observed that reacting of boron trifluoride with certain sterically hindered amines followed by treatment with hydrogen produced borane complex of the hindered amine.

In accordance with the invention, there is provided a new method to prepare borane complexes, the method comprising

- reacting a boron trifluoride complex of formula BF3· L, wherein L is a Lewis base, with a tertiary amine and hydrogen,

- reacting boron trifluoride and a Lewis base L with a tertiary amine and hydrogen, or

- reacting boron trifluoride with a tertiary amine to form a compound of formula BF3-f-Amine, wherein f-Amine is the tertiary amine, and reacting the compound of formula BFsf-Amine formed with hydrogen, in proviso that intensity of ¹⁹F NMR signal of boron trifluoride etherate does not decrease more than 90% upon admixing with equimolar amount of the tertiary amine.

In accordance with the invention, there is also provided new reagents for use in the method.

Accordingly, in one aspect the present invention concerns an admixture of a compound 15 of formula BF3 L and 1,2,2,6,6-pentamethylpiperidine, wherein L is a Lewis base.

According to another aspect, the present invention concerns a molecule of formula (I) f-Amine BF3 (I) wherein the f-Amine is selected from a group consisting of

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R³ wherein R¹, R², and R³ are same or different alkyl groups.

Various exemplifying and non-limiting embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying embodiments.

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The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also unrecited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. The terms “Lewis adduct”, “adduct”, “complex” are used interchangeably.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 shows ¹⁹F NMR spectrum of a 1:1 mixture of 1,2,2,6,6-pentamethylpiperidine and BF3· Et20 in CD2CI2, figure 2 shows ¹⁹F NMR spectrum of a 1:1 mixture of /V-ferf-butyl-A//sopropylethylamine and BF3· Et20 in CD2CI2, and figure 3 shows ¹⁹F NMR spectrum of a 1:1 mixture of /V,/V-diisopropylethylamine and BF3' Et20 in CD2CI2·

DESCRIPTION

The invention of the present disclosure concerns a method for producing borane complexes and reagents for the same.

According to one embodiment, the method comprises reacting a boron trifluoride complex of formula BF3 L, wherein L is a Lewis base, with a tertiary amine under hydrogen atmosphere.

Without binding to any theory, it is assumed that the reacting according to this embodiment occurs according to equation (2) or equation (3) depending on the nature of the Lewis base:

BF₃ L + 3 H₂ + 3 f-Amine BH₃ L + 3 L + 3 [f-AmineH]⁺[BF₄]T (2)

BF₃ L + 3 H₂ + 4 f-Amine -+ BH₃ f-Amine + 4 L + 3 [f-AmineH]⁺[BF₄]T (3) wherein L is a Lewis base, and f-Amine is the tertiary amine.

When reacting according to equation (2), the tertiary amine does not form a Lewis adduct with borane, and the Lewis base L does form a borane adduct BH3 L. Exemplary Lewis bases reacting according equation (2) are dialkyl sulfides, methyl aryl sulfides, and tetrahydrofuran. Preferable Lewis bases are dimethyl sulfide and

20165285 prh 04-04-2016 tetrahydrofuran. The most preferable Lewis base is dimethyl sulfide. A preferable tertiary amine is 1,2,2,6,6-pentamethylpiperidine.

When reacting according to equation (3), the tertiary amine is acting as a Bronsted base and a Lewis base for complexation of borane. Exemplary Lewis bases L reacting according to equation (3) are methyl ferf-butyl ether, diethyl ether, dimethyl ether. A preferable Lewis base L is diethyl ether. A preferable tertiary amine is 1,2,2,6,6pentamethylpiperidine.

According to another embodiment, the reacting is performed in the presence of two or more Lewis bases, e.g. L¹ and L². Without binding to any theory, it is assumed that io the reacting according to this embodiment occurs according to equation (4)

BF₃ L¹ + 3 BF3 L² + 3 H2 + 3 f-Amine BH₃ L¹ + 3 L² + 3 [f-AmineH]⁺[BF₄h (4) wherein L¹ and L² are Lewis bases and f-Amine is the tertiary amine.

Exemplary Lewis bases L suitable for the method according to equation (4) are L¹ : dialkyl sulfides, methyl aryl sulfides, tetrahydrofuran; and L² : methyl ferf-butyl ether, diethyl ether, dimethyl ether. The preferable Lewis bases L¹ and L² are dimethyl sulfide and diethyl ether, respectively. A preferable tertiary amine is 1,2,2,6,6pentamethylpiperidine.

According to another embodiment, the method of the present invention comprises reacting boron trifluoride and a Lewis base L with a tertiary amine under hydrogen atmosphere. Without binding to any theory, it is assumed that the reacting occurs according to equation (5):

BF₃ + L + 3 H₂ + 3 f-Amine BH₃ L + 3 [f-AmineH]⁺[BF₄n (5) wherein L is a Lewis base, and f-Amine is the tertiary amine.

Reacting according to equation (5) is preferable over reacting according any of equations (2), (3) or (4), since the reacting according to equation (5) uses the less expensive BF₃ instead of BF₃ L complexes, and the Lewis base L is not formed as a byproduct during the process. According to this embodiment the reacting is performed preferably by applying boron trifluoride gas to a solution comprising a Lewis base, such as dimethyl sulfide, and a suitable tertiary amine, followed by reacting with hydrogen.

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A preferable tertiary amine is 1,2,2,6,6-pentamethylpiperidine. The reacting is preferably performed in an inert solvent such as benzene and toluene.

According to another embodiment, the method of the present invention comprises reacting boron trifluoride and a tertiary amine under hydrogen atmosphere.

Without binding to any theory, it is assumed that the reacting occurs to equation (6):

BF₃ + 3 H₂ + 4 f-Amine BH₃ f-Amine + 3 [f-AmineH]⁺[BF₄]T (6) wherein f-Amine is the tertiary amine.

According to this embodiment the reacting is performed preferably by applying boron trifluoride gas to a solution comprising a suitable tertiary amine followed by treatment io with hydrogen. The reacting is preferably performed in an inert hydrocarbon solvent such as benzene or toluene. Herein, the tertiary amine plays a dual role of a Bronsted base and the Lewis base for complexation of borane. A preferable tertiary amine is

1,2,2,6,6-pentamethylpiperidine (PMP).

It is essential that the Lewis adduct of the tertiary amine and boron trifluoride is loose, otherwise, the too stable BF₃ f-Amine adduct formed prevents the formation of the desired borane complexes. This requirement can be evaluated by NMR analysis of the mixtures of the tertiary amines with a boron compound such as boron trifluoride diethyl etherate (BFE), and comparing the NMR spectrum of the admixture with the spectra of the corresponding individual compounds. Figures 1-3 demonstrate ¹⁹F NMR spectra of admixture of BFE and 1,2,2,6,6-pentamethylpiperidine, /V-ferf-butyl-A//sopropylethylamine, and /V,/V-diisopropylethylamine, respectively.

If the NMR spectra of BFE does not change substantially upon admixing with the tertiary amine, the amine is suitable for the method of the present invention. Accordingly, upon admixing equimolar amounts of a tertiary amine and BFE, the ¹¹B

NMR and ¹⁹F NMR spectra of the admixture should have one major ¹¹B and ¹⁹F signal of intact BFE. As shown from Figure 1, ¹⁹F NMR spectrum of the 1:1 admixture of

1,2,2,6,6-pentamethylpiperidine and BFE includes only a ¹⁹F signal of BFE.

In certain cases, an equilibrium may establish between BFE, diethyl ether, BF₃ fAmine, and f-Amine, which can be detected by NMR. If this is the case, the ¹¹B NMR and the ¹⁹F NMR spectra of the equimolar f-Amine - BFE mixture should contain two

20165285 prh 04-04-2016 major peaks. This is demonstrated in Figure 2 that shows ¹⁹F NMR spectrum of admixture of A/-fert-butyl-/\/-/sopropylethylamine.

When the ratio of intensity of the signal identified as a BF3 f-Amine adduct and that of the intensity of the BFE signal does not exceed 9:1, the tertiary amine is suitable for the method of the present invention. The lower is the mole fraction of the BF3 f-Amine adduct, the better. Preferably the ration does not exceed 4:1, more preferably 7:3, even more preferably 1:1. Further preferable ratios are 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 and 1:9.

Thus, intensity of ¹⁹F NMR signal of boron trifluoride etherate should not decrease more than 90%, preferably not more than 80%, more preferably not more than 70%, even more preferably not more than 50% upon admixing with equimolar amount of the tertiary amine. Most preferably, the intensity of ¹⁹F NMR signal of boron trifluoride etherate is substantially similar in the presence and absence of the tertiary amine, i.e. the BFE fluorine signal is the only peak in the ¹⁹F NMR spectrum of the admixture as in the case of PMP.

Table 1 shows ability of exemplary tertiary amines to form Lewis adducts studied by ¹H, ¹⁹F and ¹¹B NMR spectroscopy. NMR signals of BFE disappeared upon addition of triethylamine and diisopropylethylamine, indicating the formation of the BF3-amine Lewis adducts that are more stable than the starting BFE. As an illustrative example,

Figure 3 shows a ¹⁹F NMR spectrum of an admixture of DIPEA (N,Ndiisopropylethylamine) and BFE exhibiting a single peak of DIPEA BF3 adduct but no BFE signal. Such an amine is not suitable for use in the method of the present invention. By contrast, the NMR spectra of the mixture of PMP and BFE demonstrated substantially no difference with the NMR spectra of individual compounds, and thus this tertiary amine is suitable for the method of the present invention (figure 1). The NMR spectra of the mixture of A/-fert-butyl-/\/-/sopropylethylamine and BFE demonstrate the presence of substantial amounts of BFE, /V-ferf-butyl-A//sopropylethylamine, and boron trifluoride /V-ferf-butyl-/\/-/sopropylethylamine complex, pointing on the established equilibrium (figure 2). The ratio of the integrals of ¹⁹F NMR signals of BFE and boron trifluoride A/-fert-butyl-/V-/sopropylethylamine complex in the admixture was 4:1. Accordingly this tertiary amine is suitable for the method of the present invention.

Table 1. The ability of tertiary amines to form a Lewis adduct with BFE as determined with ¹H, ¹¹B and ¹⁹F NMR.

Tertiary Amine	k	AU k	AU k	1
forms a Lewis adduct	yes	yes	equilibrium³	no
a. ¹⁹F NMR signal of BFE decreased 20% upon addition of 1 eq. of this terl	tiary amine.

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According to a preferable embodiment, the chemical shift of ¹⁹F NMR signal of BFE 5 changes < 1 ppm upon addition of equimolar amount of the tertiary amine.

According to another preferable embodiment, the chemical shift of ¹⁹F and ¹¹B NMR signal of BFE changes < 1 ppm and <0.15 ppm, respectively, upon addition of equimolar amount of the tertiary amine.

Accordingly, exemplary tertiary amines suitable for the present method are N-tert10 butyl-/V-/'sopropylethylamine and 1,2,2,6,6-pentamethylpiperidine (PMP). A preferable amine is PMP.

The suitability of further tertiary amines for use in the method of the present invention can be verified by the NMR spectroscopic method described above.

It was observed that when PMP was treated with BF3 gas, a compound characterized 15 as BF3 PMP was formed. Thus, although PMP does not form a Lewis adduct in the presence of BFE, it does it with BF3.

According to a particular embodiment, the method of the present invention comprises reacting boron trifluoride and a tertiary amine, producing the boron trifluoride tertiary amine Lewis adduct, and its subsequent reacting with hydrogen.

Without binding to any theory, it is assumed that the reacting occurs according to equation (7) and (8):

BF3 + f-Amine —> BF3 f-Amine (7)

BF₃ f-Amine + 3 H₂ -+ BH₃ f-Amine + 3 [f-AmineH]⁺[BF₄]k (8)

According to this embodiment the reacting is performed preferably by applying boron 25 trifluoride gas to a solution of the tertiary amine in an inert hydrocarbon solvent such as benzene or toluene. The produced solution of the boron trifluoride-tertiary amine

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Lewis adducts is then exposed to hydrogen atmosphere. Herein, the tertiary amine plays a dual role of a Bronsted base and the Lewis base for complexation of borane. A preferable tertiary amine is 1,2,2,6,6-pentamethylpiperidine.

According to the method of the present invention, the reacting comprises reacting in hydrogen atmosphere. Hydrogen pressure is preferably 5-150 bar, typically 20 bar. The reacting is preferably performed in elevated temperature, preferably between 50150 °C, typically at 75 °C. According to an exemplary embodiment the reaction is performed at 75 °C in 20 bar H2.

It was also found that the side product of the method, i.e. a tetrafluoroborate salt of the tertiary amine, may precipitate from the reaction mixture. Thus it can be separated e.g. by filtration.

The tertiary amine can be liberated from the salt with an inorganic base, such as sodium hydroxide. An exemplary process for amine liberation is shown in equation (9):

[f-AmineH]⁺[BF₄]' + NaOH f-Amine + NaBF₄ + H₂O (9)

As shown from equation (9), the process of the tertiary amine liberation produces inorganic tetrafluoroborates, such as sodium tetrafluoroborate. Treatment of the inorganic tetrafluoroborates with strong acid, such as sulfuric acid, and boric acid, or boron anhydride, or other inorganic borate such as borax, recovers boron trifluoride. An exemplary process for recovery of boron trifluoride is shown in equation (10).

6 NaBF₄ + 6 H₂SO₄ + B₂O₃ 8 BF₃ + NaHSO₄ + 3 H₂O (10)

The recovery of the tertiary amine and the boron trifluoride is advantageous since these reagents can be recycled in the process gaining a viable way to converting boronoxygen compounds into borane complexes using H₂ as a hydrogen source along with bulk industrial chemicals. This allows the use of rather complex and expensive tertiary amines such as PMP.

The tertiary amine from BH₃ f-Amine adduct can be recovered by treatment with a suitable Lewis bases L such as dimethyl sulfide or tetrahydrofuran and subsequent separation, preferably by distillation. Without binding to any theory, it is assumed that the reacting occurs according to equation (11)

BH₃ f-Amine + L —> BH₃ L + f-Amine (11) wherein L is a Lewis base and f-Amine is the tertiary amine.

According to another embodiment the present invention concerns a molecule of Formula (I) f-Amine BF3 (I) wherein the f-Amine is selected from a group consisting of

and

R³ and wherein R¹, R², and R³ are same or different alkyl groups.

A preferable reagent is the molecule of Formula (II)

These molecules are suitable for use in the method of the present invention.

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According to another embodiment, the present invention concerns a method and reagents for the preparation of substituted boranes and their complexes by derivatization of the Z-H bonds into the Z-B bonds (so called Z-H borylation reaction), wherein Z is C, N, O, S, or P atom.

According to one embodiment, the reagents are admixtures of BF3L wherein L is a Lewis base, and a tertiary amine of the present invention, Exemplary Lewis bases are dimethyl sulfide, tetrahydrofuran, diethyl ether, dimethyl ether, methyl f-butyl ether.

Without binding to any theory, it is assumed that the reaction proceed according to one 20 of the equations (12)-(18) below. The outcome of the reaction depends on the nature of substrate, Lewis base L, tertiary amine f-Amine and reaction conditions:

BF₃ L + f-Amine + R_nZ-H R_nZ-BF₂ + 2 L + [f-AmineH]⁺[BF₄]- (12)

BF₃ L + f-Amine + R_nZ-H R_nZ-BF₂ L + L + [f-AmineH]⁺[BF₄]- (13)

BFs L + 2 f-Amine + 2R_nZ-H -+ (R_nZ)₂-BF L + 2 L + 2[f-AmineH]⁺[BF₄]- (14)

BF₃ L + 2 f-Amine + 2R_nZ-H -+ (R_nZ)₂-BF + 3 L + 2[f-AmineH]⁺[BF₄]- (15)

BF₃ L + 3 f-Amine + 3R_nZ-H -+ (R_nZ)₃-B L + 3 L + 3[f-AmineH]⁺[BF₄]- (16)

BF₃ L + 3 f-Amine + 3R_nZ-H -+ (R_nZ)₃-B + 4 L + 3[f-AmineH]⁺[BF₄]- (17)

4 BF₃ L + f-Amine + 4R_nZH [f-AmineH]⁺[(RnZ)₄-B]- + L + 3 [BF₄]’ (18) wherein Z is C, N, O, S, or P atom, R_n are one or several (up to five) independent organic radicals, n is in the range 1 - 5, L is a Lewis base, and f-Amine is a tertiary amine of the present invention, preferably PMP.

Exemplary non-limiting procedures for the preparation of trialkynyl boronates by C-H io borylation of terminal alkynes using the reagents of the present invention is shown in

Scheme 1.

Me₄NF (5), CH₂CI₂

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Scheme 1

Accordingly, stirring of terminal acetylenes 1 with the boron trifluoride dimethyl sulfide 15 complex and PMP in ΟθΗθ at room temperature resulted in formation of li trialkynylborane-dimethyl sulfide adducts 2 and precipitation of 1,2,2,6,6pentamethylpiperidinium tetrafluoroborate 3. With few exceptions, all the tested acetylenes furnished 2 within 2 - 6 h. After removing 3 by filtration, some of the adducts, e.g. of tri(phenylethynyl)borane 2a, were isolated in the pure form by precipitation with hexane. The characteristic broad singlets of 2 near 16 ppm appeared in the ¹¹B NMR spectra. The majority of adducts 2 were converted without isolation into trialkynylfluoroborates 4 by treatment with the solution of tetramethylammonium fluoride 5. These novel compounds were isolated as white crystalline solids in good to high overall yields.

io Exemplary non-limiting procedure for the preparation of difluoroarylboranes by sp²borylation of arenes using the reagents of the present invention is shown in Scheme

2.

Scheme 2

Exemplary non-limiting procedure for the preparation of borazines by N-H borylation of primary amines using the reagents of the present invention is shown in Scheme 3.

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RNH₂ + 9BF₃ OEt₂ + 6

R = aryl, alkyl c₆h₆ rt instantly

Scheme 3

According to another embodiment, the present invention concerns the use of reagents of Formula (I) for Z-H borylations f-Amine BF3 (I) wherein the f-Amine is selected from a group consisting of

R³ and wherein R¹, R², and R³ are same or different alkyl groups. A preferable reagent is the molecule of Formula (II) ^BF3 (II)

Without binding to any theory, it is assumed that the reaction proceed according to one of the equations (19) - (22) below. The outcome of the reaction depends on the nature of substrate, ligand L and conditions:

BF₃ f-Amine + R_nZ-H R_nZ-BF₂ + f-Amine + [f-AmineH]⁺[BF₄]- (19)

BF₃ f-Amine + 2 R_nZ-H (R_nZ)₂-BF + f-Amine + 2 [f-AmineH]⁺[BF₄]- (20)

BF₃ f-Amine + 3 R_nZ-H (R_nZ)₃-B + f-Amine + 3 [f-AmineH]⁺[BF₄]- (21)

BF₃ f-Amine + 3 R_nZ-H [f-AmineH]⁺[(RnZ)4-B]- + 3 [f-AmineH]⁺[BF4]- (22) wherein Z is C, N, O, S, or P atom, R_n are one or several (up to five) independent organic radicals, n is in the range 1 - 5, and f-Amine is a suitable tertiary amine, preferably PMP.

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Exemplary non-limiting procedures for the preparation of trialkynyl boranes by C-H borylation of terminal alkynes using the reagent of Formula (II) is shown in Scheme 4.

Scheme 4

Exemplary non-limiting procedure for the preparation of difluoroarylboranes by sp²20 borylation of arenes using the reagent of Formula (II) is shown in Scheme 5.

Scheme 5

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According to another embodiment, the present invention concerns the simultaneous use of reagents of Formula (II) and boron trifluoride complexes BF3 L for Z5 borylations, wherein L is a Lewis base.

Without binding to any theory, it is assumed that the reaction proceed according to one of the equations (23) - (28) below. The outcome of the reaction depends on the nature of substrate, ligand L and reaction conditions:

BF₃ f-Amine + BF₃ L + R_nZ-H -+ R_nZ-BF₂ + L + [f-AmineH]⁺[BF₄]’ (23)

BF₃ f-Amine + BF₃ L + R_nZ-H -+ R_nZ-BF₂ L + [f-AmineH]⁺[BF₄]- (24)

BF₃ f-Amine + BF₃ L + 2 R_nZ-H (R_nZ)₂-BF + L + 2 [f-AmineH]⁺[BF₄]- (25)

BF₃ f-Amine + BF₃ L + 2 R_nZ-H (R_nZ)₂-BF L + 2 [f-AmineH]⁺[BF₄]- (26)

BF₃ f-Amine + BF₃ L + 3 R_nZ-H (R_nZ)₃-B + L + 3 [f-AmineH]⁺[BF₄]- (27)

BF₃ f-Amine + BF₃ L + 3 R_nZ-H (R_nZ)₃-B L + 3 [f-AmineH]⁺[BF₄]- (28) wherein Z is C, N, O, S, or P atom, R_n are one or several (up to five) independent organic radicals, n is in the range 1 - 5, L is a Lewis base, and f-Amine is a tertiary amine according to the present invention, preferably PMP.

Further embodiments of the present invention are disclosed in the following numbered clauses.

1. A method for producing trialkynyl boronates, the method comprising:

- proving an admixture comprising a molecule of formula BF₃ L and 1-alkyl-2,2,6,6tetramethylpiperidine, preferably 1,2,2,6,6-pentamethylpiperidine, wherein L is a Lewis base, and

- reacting the admixture with a reagent of formula (III) (m) wherein X is a substituent comprising an alkyl group an/or an aryl group, and wherein the Lewis base L is preferably selected from a group consisting of dialkyl sulfide, aryl alkyl sulfide, tetrahydrofuran, diethyl ether, dimethyl ether, methyl ferf-butyl ether and mixtures thereof, preferably from dimethyl sulfide and diethyl ether and mixtures thereof.

2. The method according to clause 1, the method further comprising treating with tetraalkylammonium fluoride.

3. The method according to clause 1 or 2, wherein X is selected from io and and wherein — is the position of the alkynyl group.

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4. A method for producing trialkynyl boronates, the method comprising:

reacting a compound of formula (I) f-Amine BF3 (I) wherein the f-Amine is selected from a group consisting of

N

I

R¹

and _R2 wherein R¹, R², and R³ are independently alkyl groups, with a reagent of formula (III)

X^= (III) wherein X is a substituent comprising alkyl group or aryl group.

5. The method according to clause 4, the method further comprising treating with tetraalkylammonium fluoride.

6. The method according to clause 4 or 5, wherein X is selected from

and wherein — is the position of the alkynyl group.

io 7. A compound of formula (IV)

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(IV) wherein X is a substituent comprising alkyl and/or aryl group.

8. The compound according to clause 7, wherein X is selected from

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and wherein — is the position of the alkynyl group.

8. A method for conversion of Z-H-bond into Z-B bond, wherein Z is selected from C, N, O, S and P, the method comprising

- reacting boron trifluoride complex of formula BF3L, wherein L is a Lewis base, with a tertiary amine and a compound comprising Z-H bond,

- reacting boron trifluoride and a Lewis base L with a tertiary amine and a compound comprising Z-H bond or

- reacting compound of formula BF3· f-Amine with and a compound comprising Z-H 10 bond, in proviso that intensity of ¹⁹F NMR signal of boron trifluoride etherate does not decrease more than 90% upon admixing with equimolar amount of the tertiary amine.

9. The method according to clause 8, wherein the tertiary amine is selected from a group consisting of

wherein R¹, R², and R³ are independently alkyl groups.

10. The method according to clause 9, wherein the tertiary amine is 1,2,2,6,6pentamethylpiperidine.

11. The method according to any of claims 8 to 10, wherein the Lewis base L is selected from a group consisting of dialkyl sulfide, aryl alkyl sulfide, tetrahydrofuran, diethyl ether, dimethyl ether, methyl tert-butyl ether and mixtures thereof, preferably from dimethyl sulfide and diethyl ether and mixtures thereof.

Examples

Example 1. Evaluation of the tertiary amine for suitability for the preparation of boranes.

A typical procedure.

1,2,2,6,6-pentamethylpiperidine and BFE:

(1) A solution of 1,2,2,6,6-pentamethylpiperidine in CD2Cl2was prepared, and ¹H NMR io spectrum was recorded at 27 °C in a 500 MHz instrument.

(2) A solution of BFE in CD2Cl2was prepared, and ¹H, ¹⁹F, and ^{4 * * * * * * 11 * *}B NMR spectra were recorded at 27 °C in the instrument. ¹¹B NMR, CD2Cl2,6, ppm: 0.0 (s), ¹⁹F NMR, CD2CI2, 5, ppm: -153.2 (s).

(3) 1:1 molar mixture of 1,2,2,6,6-pentamethylpiperidine and BFE in CD2CI2 was prepared and ¹H, ¹⁹F, and ¹¹B NMR spectra were recorded at 27 °C in the instrument.

¹¹B NMR, CD₂Cl2,6, ppm: 0.0 (s), ¹⁹F NMR, CD2CI2, δ, ppm: -153.2 (s).

(4) Comparison of spectra of the individual components (1) and (2), and their mixture (3) revealed no essential difference. Since the spectra obtained from the mixture did not differ from the spectra of the separate components, 1,2,2,6,620 pentamethylpiperidine is not able to form the boron trifluoride complex upon treatment with BFE and thus it is suitable for use in the method.

A/-fert-butyl-/\/-/sopropylethylamine and BFE:

(1) ¹H NMR spectrum of /V-fert-butyl-/\/-/sopropylethylamine in CD2Cl2was prepared, and ¹H NMR spectrum was recorded at 27 °C in a 500 MHz instrument.

(2) A solution of BFE in CD2Cl2was prepared, and ¹H, ¹⁹F, and ¹¹B NMR spectra were recorded at 27 °C in the instrument. ¹¹B NMR, CD2Cl2,6, ppm: 0.0 (s), ¹⁹F NMR, CD2CI2, δ, ppm: -153.2 (s).

(3) 1:1 molar mixture of A/-fert-butyl-/V-/sopropylethylamine and BFE in CD2CI2 was prepared and ¹H, ¹⁹F, and ¹¹B NMR spectra were recorded at 27 °C in the instrument,

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20165285 prh 04-04-2016 revealing appearing of boron trifluoride A/-ferf-butyl-A/-/sopropylethylamine complex in equilibrium with BFE in the ratio 1:4 by ¹⁹F NMR. The signals of boron trifluoride N-tertbutyl-/V-/sopropylethylamine complex: ¹¹B NMR, CD2CI2, δ, ppm: 0.5 (br. s.), ¹⁹F NMR, CD2CI2, δ, ppm: -136.8 (s).

(4) Spectra of the individual components (1) and (2), and their mixture (3) were compared. Since the intensity of the BFE signal in the ¹⁹F NMR spectrum of the mixture constitutes 80% of the total intensity that is above 10%, /V-ferf-butyl-A//sopropylethylamine forms loose adduct with boron trifluoride and thus is suitable for use in the method.

/V,/V-diisopropylethylamine and BFE:

(1) ¹H NMR spectrum of /V,/V-diisopropylethylamine in CD2Cl2was prepared, and ¹H NMR spectrum was recorded at 27 °C in a 500 MHz instrument.

(2) A solution of BFE in CD2Cl2was prepared, and ¹H, ¹⁹F, and ¹¹B NMR spectra were recorded at 27 °C in the instrument. ¹¹B NMR, CD2Cl2,6, ppm: 0.0 (s), ¹⁹F NMR, CD2CI2, δ, ppm:-153.2 (s).

(3) 1:1 molar mixture of /V,/V-diisopropylethylamine and BFE in CD2CI2 was prepared and ¹H, ¹⁹F, and ¹¹B NMR spectra were recorded at 27 °C in the instrument. ¹¹B NMR, CD2CI2, δ, ppm: 0.3 (q, Ubf = 19.9 Hz), ¹⁹F NMR, CD2CI2, δ, ppm: -142.2 (q, Ubf = 19.9 Hz).

(4) Spectra of the individual components (1) and (2), and their mixture (3) were compared. Since the spectra obtained from the mixture did differ from the spectra of the separate components, diisopropylethylamine forms the boron trifluoride complex upon treatment with BFE and thus it not suitable for use in the method.

Example 2. Comparative example, use of /V./V-diisopropylethylamine instead of

1,2,2,6,6-tetramethylpiperidine

A gas-tight high-pressure NMR tube was charged with 20 mg of N,Ndiisopropylethylamine (0.16 mmol), 22 mg of boron trifluoride diethyl ether complex (0.16 mmol) and 0.2 ml of CD2CI2, and then pressurized with 11 bar of H2 (>0.5 mmol). The NMR tube was heated in an oil bath at 80 °C for 24 h. The tube content was analyzed with ¹H, ¹¹B and ¹⁹F NMR spectroscopy revealing no reaction with H2.

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Example 3. Preparation of borane dimethyl sulfide complex g of 1,2,2,6,6-tetramethylpiperidine (12.9 mmol), 2.23 g of boron trifluoride dimethyl sulfide complex (17.2 mmol) and 20 ml of toluene were placed in a 300 ml stainless steel autoclave under Ar atmosphere. The autoclave was charged with 20 bar of hydrogen and heated for 4 h at 75 °C with magnetical stirring. After cooling down and releasing hydrogen, the reaction mixture consisted of a crystalline precipitate of

1,2,2,6,6-tetramethylpiperidinium tetrafluoroborate and a supernatant liquid. ¹¹B NMR analysis of the supernatant liquid revealed complete consumption of the initial boron trifluoride dimethyl sulfide complex and the presence of borane dimethyl sulfide io complex as a major (>90 mol. %) component.

Example 4. Preparation of borane dimethyl sulfide complex g of 1,2,2,6,6-tetramethylpiperidine (12.9 mmol), 0.56 g of boron trifluoride dimethyl sulfide complex (4.3 mmol), 1.83 g of boron trifluoride diethyl ether complex (12.9 mmol), and 11 ml of toluene were placed in a 300 ml stainless steel autoclave under

Ar atmosphere. The autoclave was charged with 20 bar of hydrogen and heated for 2 h at 100 °C with magnetical stirring. After cooling down and releasing hydrogen, the reaction mixture consisted of a crystalline precipitate of 1,2,2,6,6tetramethylpiperidinium tetrafluoroborate and a supernatant liquid. ¹¹B NMR analysis of the supernatant liquid revealed a mixture of 40 mol. % of boron trifluoride diethyl ether complex and 60 mol. % of borane dimethyl sulfide complex.

Example 5. Preparation of BH3 PMP adduct g of 1,2,2,6,6-tetramethylpiperidine (12.9 mmol), 1.83 g of boron trifluoride diethyl ether complex (12.9 mmol), and 10 ml of benzene were placed in a 300 ml stainless steel autoclave under Ar atmosphere. The autoclave was charged with 30 bar of hydrogen and heated for 2 h at 100 °C with magnetical stirring. After cooling down and releasing hydrogen, the reaction mixture consisted of a crystalline precipitate of

1,2,2,6,6-tetramethylpiperidinium tetrafluoroborate and a supernatant liquid. ¹¹B NMR analysis of the supernatant liquid revealed a mixture of 20 mol. % of boron trifluoride diethyl ether complex, 60 mol. % of borane 1,2,2,6,6-pentamethylpiperidine complex, and 20 mol. % of borane 2,2,6,6-tetramethylpiperidine complex.

Example 6. Preparation of BF3 PMP adduct

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A solution of 2 g of 1,2,2,6,6-pentamethylpiperidine in 10 ml of cyclohexane was exposed to 1.5 bar of gaseous BF3 in a 200 ml Schlenk tube. After stirring for 10 min a tick white precipitate formed. The volatiles were evaporated in vacuum furnishing boron trifluoride 1,2,2,6,6-pentamethylpiperidine complex as a white solid in a quantitative yield . ¹H NMR, 500 MHz, Οθϋβ, δ, ppm: 1.14 (m, 4H), 1.20 (m, 2H), 1.28 (s, 12H), 2.22 (s, 3H); ¹³C NMR, 75 MHz, CD2CI2, δ, ppm: 67.41, 37.00, 36.37, 29.69, 17.07. ¹¹B NMR, C6D6, δ, ppm: 1.0 (s), ¹⁹F NMR, C6D₆, δ, ppm: -135.8 (s).

Example 7. Preparation of BF3 PMP adduct from boron trifluoride dimethyl sulfide complex

A 25 ml Schlenk tube was charged with 1 g of 1,2,2,6,6-pentamethylpiperidine, 5 ml of dichloromethane and 870 g of boron trifluoride dimethyl sulfide complex. The volatiles were evaporated in vacuum furnishing boron trifluoride 1,2,2,6,6pentamethylpiperidine complex as a white solid in a quantitative yield.

Example 8. Preparation of boron trifluoride /V-te/i-butyl-/\/-/sopropvlethvlamine adduct from boron trifluoride dimethyl sulfide complex

A 25 ml Schlenk tube was charged with 920 mg of A/-tert-butyl-/\/-/sopropylethylamine, 5 ml of dichloromethane and 870 g of boron trifluoride dimethyl sulfide complex. The volatiles were evaporated in vacuum furnishing boron trifluoride Ndert-buty\-N/sopropylethylamine complex in a quantitative yield. ¹H NMR, 500 MHz, CD2CI2, δ, ppm: 3.64 (hept, 1H), 2.99 (q, 2H), 1.60 - 1.00 (m, 17H); ¹³C NMR, 75 MHz, , CD2CI2, δ, ppm: 46.68, 29.07, 22.43, 20.50, 11.73. ¹¹B NMR, CD2CI2, δ, ppm: 0.5 (br.s), ¹⁹F NMR, CD2CI2, δ, ppm: -136.9 (s).

Example 9. Preparation of boron trifluoride /V,/V-diisopropvl-/so-butvlamine adduct from boron trifluoride dimethyl sulfide complex

A 25 ml Schlenk tube was charged with 1 g of /V,/V-diisopropyl-/so-butylamine, 5 ml of dichloromethane and 870 g of boron trifluoride dimethyl sulfide complex. The volatiles were evaporated in vacuum furnishing boron trifluoride /V,/V-diisopropyl-/so-butylamine complex in a quantitative yield. ¹H NMR, 500 MHz, Οβϋθ, δ, ppm: 3.69 (hept, J = 6.4 Hz, 2H), 2.75 (m,2H), 1.32 (m, 12H), 1.04 (d, J = 6.6 Hz, 6H), 1.00 (m, 1H). ¹³C NMR,

75 MHz, CD2CI2, δ, ppm: 56.80, 55.61, 24.30, 23.99, 21.09, 20.24, 19.79. ¹¹B NMR,

C₆D₆, δ, ppm: 0.8 (q, J = 20 Hz), ¹⁹F NMR, C₆D₆, δ, ppm: -140.84 (q, J = 20 Hz).

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Example 10. Preparation of BH3 PMP adduct.

g of 1,2,2,6,6-tetramethylpiperidine (12.9 mmol), in 15 ml of benzene were exposed to 1.5 bar of boron trifluoride in 200 ml Schlenk tube. The tube was flashed with argon and the solution of boron trifluoride 1,2,2,6,6-pentamethylpiperidine complex was placed in a 300 ml stainless steel autoclave under Ar atmosphere. The autoclave was charged with 20 bar of hydrogen and heated for 1.5 h at 75 °C with magnetical stirring. After cooling down and releasing hydrogen, the reaction mixture consisted of a crystalline precipitate of 1,2,2,6,6-tetramethylpiperidinium tetrafluoroborate and a supernatant liquid. ¹¹B NMR analysis of the supernatant liquid revealed no starting boron trifluoride 1,2,2,6,6-pentamethylpiperidine complex, 60 mol. % of borane

1,2,2,6,6-pentamethylpiperidine complex, and other minor B-H derivatives.

Example 11. Preparation of tris(phenvlethvnyl)borane dimethyl sulfide adduct

306 mg of phenylacetylene (3 mmol, 1 eq.), 465 mg (3 mmol, 1 eq.) of 1,2,2,6,6pentamethylpiperidine, 520 mg (4 mmol, 1.33 eq.) of boron trifluoride dimethyl sulfide were stirred in 6 ml of dry benzene in a 25 ml Schenk tube for 24 h under argon atmosphere. The produced precipitate of 1,2,2,6,6-pentamethylpiperidinium tetrafluoroborate was filtered, washed with 3 ml of benzene, and discarded. The mother liquor was treated with 12 ml of dry hexane causing precipitation of the target compound as a white solid. Filtration, drying in vacuum furnished 281 mg (76.5%). ¹H

NMR (300 MHz, CD2CI2) δ 7.53 (6H, m), 7.35 (9H, m), 2.53 (6H, s). ¹¹B NMR (160 MHz, CD2CI2) δ -15.78. ¹³C NMR (75 MHz, CD2CI2) δ 131.9 (6), 128.4 (6), 128.1 (4), 124.5 (4), 98.8 (3), 94.6 (3), 20.2 (2).

Example 12. Preparation of tetramethylammonium trialkynylfluoroborates, general protocol

A terminal acetylene (4 mmol, 1 eq.), 620 mg (4 mmol, 1 eq.) of 1,2,2,6,6pentamethylpiperidine, 692 mg (5.32 mmol, 1.33 eq.) of boron trifluoride dimethyl sulfide were stirred in 6 ml of benzene for 15 h at room temperature. The produced precipitate was filtered, washed with 3 ml of benzene and discarded. The filtrate was treated with a solution of 112 mg (1.2 mmol, 0.30 eq.) of tetramethylammonium fluoride in 3 ml of dichloromethane. The reaction was additionally stirred for 6 h and evaporated in vacuum. The solid residue was washed with 4 ml of benzene, and the filtrate was discarded. The filter cake was redissolved in dichloromethane and filtered. The filtrate

20165285 prh 04-04-2016 was evaporated giving the target tetramethylammonium trialkynylfluoroborate as a white solid.

Tetramethylammonium fluorotri(hex-1 -yn-1 -vDborate.

Yield 83%. ¹H NMR (300 MHz, CD2CI2) δ 3.35 (12H, s), 2.12 (6H, t, 7=7.4 Hz), 1.41 5 (12H, m), 0.90 (9H, t, 7=6.9 Hz). ¹¹B NMR (160 MHz, CD2CI2,) δ -12.52. ¹³C NMR (75

MHz, CD2CI2) δ 97.0 (br), 92.9 (m), 56.5 (t, 7=3.9 Hz), 32.2, 22.4, 19.9, 13.7. ¹⁹F NMR (160 MHz, CD2CI2) δ -180.06.

Tetramethylammonium fluorotris(phenvlethvnyl)borate.

Yield 82 %. ¹H NMR (500 MHz, CD2CI2) δ 7.40 (6H, d, J=7.2 Hz), 7.28 (6H, t, J=7.2 10 Hz), 7.23 (3H, t, J=7.2 Hz), 3.18 (12H, s). ¹¹B NMR (160 MHz, CD2CI2,) δ -11.68. ¹³C

NMR (75 MHz, CD2CI2) δ 131.5, 128.5, 127.0, 126.1, 107.0 (br), 93.9,56.3 (t, 7=3.9 Hz). ¹⁹F NMR (160 MHz, CD2CI2) δ -185.97.

Tetramethylammonium fluorotris(p-tolvlethvnyl)borate.

Yield 82 %. ¹H NMR (500 MHz, CD2CI2) δ 7.28 (6H, d, J=7.8 Hz), 7.09 (6H, d, J=7.8 15 Hz), 3.21 (12H, s), 2.32 (9H, s). ¹¹B NMR (160 MHz, CD2CI2) δ -11.71. ¹³C NMR (75

MHz, CD2CI2) δ 137.0, 131.3, 129.2, 123.1, 106.2 (br), 93.9, 56.3 (4, t, 7=3.9 Hz), 21.2. ¹⁹F NMR (160 MHz, CD2CI2) δ -185.11.

Tetramethylammonium fluorotris((4-methoxyphenvl)ethvnvl)borate.

Yield 84 %. ¹H NMR (500 MHz, CD2CI2) δ 7.32 (6H, d, J=8.8 Hz), 6.82 (6H, d, J=8.8 20 Hz), 3.78 (9H, s), 3.22 (12H, s). ¹¹B NMR (160 MHz, CD2CI2) δ -11.69. ¹³C NMR (75

MHz, CD2CI2) δ 158.7, 132.7, 118.3, 114.0, 105.2 (br), 93.5 (d, J=6.2 Hz), 56.3 (t, 7=3.9 Hz), 55.4. ¹⁹F NMR (160 MHz, CD2CI2) δ -184.60.

Tetramethylammonium fluorotris((4-fluorophenvl)ethvnyl)borate.

Yield 77.1 %. ¹H NMR (500 MHz, CD2CI2) δ 7.40 (6H, dd, 7=8.9, 5.6 Hz), 6.99 (6H, t, 25 7=8.9 Hz), 3.28 (12H, s). ¹¹B NMR (160 MHz, CD2CI2) δ -11.82. ¹³C NMR (126 MHz,

CD2CI2) δ 161.8 (d, 7=246.5 Hz), 133.2 (dd, 7=8.0, 1.5 Hz), 122.3 (dd, 7=3.5, 1.5 Hz), 115.4 (d, 7=21.9 Hz), 108.3-103.4 (br), 92.8, 94.6, 56.4 (t, 7=3.9 Hz). ¹⁹F NMR (160 MHz, CD2CI2) δ -114.66 (3F, m), -185.94 (1F, s, br).

Tetramethylammonium tris((4-cvanophenvl)ethvnyl)fluoroborate.

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Yield 29 %. ¹H NMR (300 MHz, DMSO-de) δ 7.72 (6H, d, J=8.1 Hz), 7.47 (6H, d, J=8.1 Hz), 3.09 (12H, s). ¹¹B NMR (160 MHz, CD2CI2) δ -11.69. ¹³C NMR (75 MHz, DMSOde) δ 132.9, 132.3, 131.4, 119.5, 113.7 (br), 109.5, 92.6 (m), 55.1 (t, J=3.9 Hz). ¹⁹F NMR (160 MHz, DMSO-de) δ -191.30.

Tetramethylammonium fluorotris((4-(methoxvcarbonvl)phenvl)ethvnyl)borate.

Yield 64 %. ¹H NMR (500 MHz, CD2CI2) δ 7.91 (6H, d, J=8.3 Hz), 7.47 (6H, d, J=8.3 Hz), 3.86 (9H, s), 3.28 (12H, s). ¹¹B NMR (160 MHz, CD2CI2) δ -11.89. ¹³C NMR (75 MHz, CD2CI2) δ 166.7, 131.5, 130.8, 129.5, 128.5, 110.3 (br), 93.7 (d, J=4.8 Hz), 56.3 (t, J=3.9 Hz), 52.1. ¹⁹F NMR (160 MHz, CD2CI2) δ -187.58.

io Tetramethylammonium tris((2-chlorophenvl)ethvnyl)fluoroborate.

Yield 80 %. ¹H NMR (500 MHz, CD2CI2) δ 7.48 (3H, d, J=7.4 Hz), 7.35 (3H, d, J=7.4 Hz), 7.18 (6H, m), 3.23 (12H, s). ¹¹B NMR (160 MHz, CD2CI2) δ-11.54. ¹³C NMR (75 MHz, CD2CI2) δ 135.1, 133.7, 129.2, 128.2, 126.8, 125.5, 112.6 (br), 90.8 (m), 56.6 (t, J=3.9 Hz). ¹⁹F NMR (160 MHz, CD2CI2) δ -187.17.

Tetramethylammonium tris((3₁5-bis(trifluoromethvl)phenvl)ethvnyl)fluoroborate.

Yield 56 %. ¹H NMR (500 MHz, CD2CI2) δ 7.93 (6H,s), 7.74 (3H, s), 3.30 (12H, s). ¹¹B NMR (160 MHz, CD2CI2) δ -11.95. ¹³C NMR (75 MHz, CD2CI2) δ 131.7, 131.7 (q, J=33.3 Hz), 128.2 (m), 123.5 (q, J=272.7 Hz), 120.3 (hept, J=4.6 Hz), 109.6 (s, br), 91.3 (s), 56.5 (t, J=4.0 Hz). ¹⁹F NMR (160 MHz, CD2CI2) δ -63.89 (18), -189.60.

Tetramethylammonium tris(cvclohexvlethvnyl)fluoroborate.

Yield 72 %. ¹H NMR (300 MHz, CD2CI2) δ 3.35 (12H, s), 2.22 (3H, m), 1.74 (12H, m), 1.54 (3H, m), 1.26 (15H, m). ¹¹B NMR (160 MHz, CD2CI2) δ -12.18. ¹³C NMR (126 MHz, CD2CI2) δ 97.4 (d, J=6.3 Hz), 96.7 (br), 56.6 (t, J=3.9 Hz), 34.2, 30.7, 26.2, 25.7. ¹⁹F NMR (160 MHz, CD2CI2) δ -178.24.

Tetramethylammonium tris(3_l3-dimethylbut-1 -yn-1 -vDfluoroborate.

Yield 79 %. ¹H NMR (500 MHz, CD2CI2) δ 3.37 (12H, s), 1.19 (27H, s). ¹¹B NMR (160 MHz, CD2CI2) δ -12.12. ¹³C NMR (75 MHz, CD2CI2) δ 101.4 (m), 94.9 (br), 56.7 (t, J=3.9 Hz), 31.8, 27.8. ¹⁹F NMR (160 MHz, CD2CI2) δ -178.03.

Example 11. Preparation of 2_l4_l6-trifluoro-1_l3_l5-triphenyl-borazine

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18.6 mg of aniline (0.2 mmol), 85 mg of boron trifluoride diethyl ether complex (0.6 mmol) and 62 mg of 1,2,2,6,6-pentamethylpiperidine were stirred for 10 min in 1 ml of benzene under argon atmosphere. The precipitate was filtered and washed with 1 ml of benzene. The filtrate was evaporated in vacuum furnishing 23 mg of the target compound (95%). ¹H NMR (500 MHz, C6D6) δ 7.13 (m, 6H), 7.05 (m, 6H), 7.00 (m, 3H). ¹³C NMR (126 MHz, C6D₆) δ 138.98, 129.16, 127.42, 126.29. ¹¹B NMR (160 MHz, C6D6) δ 23.9 (s). ¹⁹F NMR (160 MHz, C6D₆) δ -120.5 (s, 3F).

Example 13. Preparation of tri(hex-1-vn-1-yl)borane

In a glove box, a 2 ml vial was charged with 16.4 mg of hex-1-yne (0.2 mmol), 60 mg io of boron trifluoride 1,2,2,6,6-pentamethylpiperidine complex (0.27 mmol) and 0.6 ml of

Οβϋδ. After 12 h of stirring at room temperature, a crystalline precipitate formed. The supernatant liquid was trasnfered into an NMR tube and analyzed by ¹H, ¹¹B and ¹³C NMR. The tri(hex-1-yn-1-yl)borane was present as the major component along with minor amount of a byproduct, 1,2,2,6,6-pentamethylpiperidine. ¹H NMR (500 MHz,

C₆D₆) δ 2.07 (t, J = 6.8 Hz, 6H), 1.32 - 1.13 (m, 12H), 0.67 (t, J = 6.8 Hz, 9H). ¹¹B NMR (160 MHz, CeDe) δ 34.3 (br.s).

Example 14. Preparation of 3-(difluoroboranyl)-1-methyl-1 H-indole

A gas-tight NMR tube was charged with 20 mg of /V-methylindole (0.15 mmol), 44 mg of boron trifluoride 1,2,2,6,6-pentamethylpiperidine complex (0.2 mmol) and 0.05 ml of

Οβϋδ. The tube was heated in an oil bath for 8 h at 80 °C. 0.4 ml of CeD6 were added, and the sample was analyzed with ¹H, ¹¹B and ¹⁹F NMR revealing a complete consumption of the starting boron trifluoride 1,2,2,6,6-pentamethylpiperidine complex and the presence of 3-(difluoroboranyl)-1-methyl-1 H-indole as the major product (>50 % of the boron-containing species). ¹H NMR (500 MHz, Οβϋβ) δ 8.10 (d, J = 7.9 Hz,

1H), 7.24 (m, 1H), 7.20 (m, 1H), 6.96 (s, 1H), 6.88 (d, J = 8.0 Hz), 2.70 (s, 3H). ¹¹B

NMR (160 MHz, C₆D₆) δ 24.3 (s). ¹⁹F NMR (160 MHz, C₆D₆) δ -93.4 (br. s).

Example 15. Preparation of 3-(difluoroboranyl)-1-methyl-1 H-indole

A gas-tight NMR tube was charged with 20 mg of /V-methylindole (0.15 mmol), 26 mg of boron trifluoride dimethyl sulfide complex (0.2 mmol), 15.5 mg of 1,2,2,6,630 pentamethylpiperidine (0.1 mmol) and 0.05 ml of Οβϋδ. The tube was heated in an oil bath for 8 h at 80 °C. 0.4 ml of Οβϋθ were added, and the sample was analyzed with ¹H, ¹¹B and ¹⁹F NMR revealing a complete consumption of the starting boron trifluoride dimethyl sulfide complex and the presence of 3-(difluoroboranyl)-1-methyl-1 H-indole as the major product (>60 % of the boron-containing species). ¹H NMR (500 MHz, C₆D₆) δ 8.10 (d, J = 7.9 Hz, 1H), 7.24 (m, 1H), 7.20 (m, 1H), 6.96 (s, 1H), 6.88 (d, J =

8.0 Hz), 2.70 (s, 3H). ¹¹B NMR (160 MHz, C6D6) δ 24.3 (s). ¹⁹F NMR (160 MHz, C6D₆) δ -93.4 (br. s).

The specific examples provided in the description given above should not be construed as limiting the scope and/or the applicability of the appended claims.

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20165285 prh 29 -03- 2018

Claims

A process for the preparation of a borane complex comprising

- selecting a tertiary amine where the ¹⁹ F NMR signal intensity of boron trifluoride etherate does not decrease by more than 90% when mixed with equivalent molar

5 with the amount of tertiary amine in question,

- reacting a boron trifluoride complex of the formula BF3L where L is a Lewis base with said tertiary amine and hydrogen,

- reacting boron trifluoride and Lewis base L with said tertiary amine and hydrogen, or

Reacting 10-boron trifluoride with said tertiary amine to form a compound of formula BF3 · f-Amine, wherein f-Amine is said tertiary amine, and reacting the thus formed compound of formula BF3 · f-Amine with hydrogen.

Method according to Claim 1, characterized in that the ¹⁹ NMR signal of boron trifluoride etherate ¹⁹ is not substantially reduced by mixing an equivalent molar amount of

15 with the tertiary amine.

The process according to claim 2, characterized in that the chemical shift of the ¹⁹ F NMR signal of boron trifluoride etherate changes by ≤1 ppm when mixed with an equivalent molar amount of the tertiary amine.

Process according to any one of claims 1 to 3, characterized in that Lewis

L 20 is selected from the group consisting of dialkyl sulfide, arylalkyl sulfide, tetrahydrofuran, diethyl ether, dimethyl ether methyl tert-butyl ether and mixtures thereof, preferably dimethyl sulfide and diethyl ether and mixtures thereof.

Process according to any one of claims 1 to 4, characterized in that the tertiary amine is 1,2,2,

6,6-pentametyylpiperidiini.

6. A process according to any one of claims 1-5, wherein the tertiary amine is 1,2,2,6,6-pentamethylpiperidine and wherein the reaction comprises reacting the tertiary amine with boron trifluoride prior to reaction with Lewis base L and hydrogen.

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Process according to any one of claims 1 to 6, characterized in that the reaction is carried out at a temperature of 30-150 ° C, preferably 30-100 ° C, most preferably 75 ° C.

Process according to any one of claims 1 to 7, characterized in that the hydrogen pressure is 5 to 150 bar, preferably 20 bar.

5

Process according to any one of claims 1 to 8, characterized in that the borane complex is a borane dimethylsulfide complex.

Process according to any one of claims 1 to 9, characterized in that the reaction produces a tetrafluoroborate salt of a tertiary amine, and wherein the process further comprises isolating the tetrafluoroborate salt of the tertiary amine, preferably by filtration.

The process according to claim 10, comprising treating the tetrafluoroborate salt of an isolated tertiary amine with an inorganic base to prepare a tertiary amine and an inorganic tetrafluoroborate.

Process according to Claim 11, characterized in that the process comprises treating inorganic tetrafluoroborate with a strong acid such as sulfuric acid and inorganic boronate to prepare boron trifluoride.

A mixture comprising a molecule of formula BF3 · L and 1,2,2,6,6pentamethylpiperidine wherein L is a Lewis base.

A mixture according to claim 13, characterized in that the Lewis base is selected from the group consisting of dialkyl sulfide, arylalkyl sulfide, tetrahydrofuran, diethyl ether, dimethyl ether methyl tert-butyl ether and mixtures thereof, preferably dimethyl sulfide.

15. A molecule of formula (I) f-Amine BF3 (I) characterized in that the f-Amine is selected from the group consisting of wherein R ¹ , R ² , and R ³ are the same or different alkyl groups.

16. The molecule of claim 15, wherein the f-Amine is 1,2,2,6,6 pentamethylpiperidine.

Use of a mixture according to claim 13 or 14 or a molecule according to claim 15 or 16 5 for the preparation of borane complexes.

20165285 prh 05 -04- 2018

1/2 fM yn

DE j DI β

-120

-140 fl {shake