Use for Boron Formates for Reducing Unsaturated Organic Functions

Abstract

The present invention relates to a method for reducing unsaturated organic compounds chosen from the group formed by the aldehydes, the ketones, the imines, the carboxylic acids, the amides, and the esters with a boron formate having the formula (I) in the presence of a solvent and optionally a base.

The invention also relates to the use of the method for reducing unsaturated organic compounds chosen from the group formed by the aldehydes, the ketones, the imines, the carboxylic acids, the amides, and the esters according to the invention in the preparation of methanol, methylated amines, formaldehyde and alcohols; for the preparation of reactants for Suzuki coupling reactions; and in the manufacturing of vitamins, pharmaceutical products, glues, acrylic fibres, synthetic leather, pesticides.

Claims

1. A method for reducing unsaturated organic compounds chosen from the group formed by the aldehydes, the ketones, the imines, the carboxylic acids, the amides, and the esters, wherein said unsaturated organic compound is reacted with a boron formate having the formula (I) ##STR00006## in which R.sup.1 and R.sup.2, independently of one another, are chosen from the group formed by a hydroxyl group, an alkoxy group, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a heterocyclic group, a halogen atom, a silyl group, a siloxy group, a phosphino group, and an amino group, said alkyl, alkenyl, alkynyl, alkoxy, silyl, siloxy, aryl, phosphino and amino groups being optionally substituted; or R.sup.1 and R.sup.2 taken together with the boron atom to which they are bonded, form an optionally substituted heterocycle; X is chosen from the group formed by a halogen atom, a carboxylate group, a sulfonate group, a hydroxyl group, an alkoxy group, an alkyl group, an alkenyl group, an alkynyl group, a heteroaryl group, a heterocyclic group, a silyl group, Z is a cation chosen from the group formed by a protonated organic base having a pKa greater than 3.7 chosen from example from the group formed by triethylammonium (HNEt.sub.3.sup.+), di-isopropylethylammonium (i-Pr.sub.2EtNH.sup.+), 2,2,6,6-tetramethylpiperidinium (TMPH.sup.+), and tricyclohexylphosphonium (HPCy.sub.3.sup.+); Na.sup.+; Li.sup.+; K.sup.+; Cs.sup.+; tetraphenylphosphonium (PPh.sub.4.sup.+); tetramethylammonium (NMe.sub.4.sup.+); tetraethylammonium (NEt.sub.4.sup.+); tetrabutylammonium (NBu.sub.4.sup.+) and tetraphenylammonium (NPh.sub.4.sup.+); n is a whole number equal to 1; in the presence of a solvent and optionally an organic or inorganic base.

2. The method according to claim 1, wherein the aldehydes, the ketones, the carboxylic acids and the esters, are reduced into alcohols; the imines are reduced into amines; and the amides are reduced into amines or into alcohols.

3. The method according to claim 1, wherein in the boron formate having the formula (I), R.sup.1 and R.sup.2, independently of one another, are chosen from the group formed by an alkyl group comprising 1 to 12 atoms of carbon; an aryl comprising 6 to 20 atoms of carbon, said alkyl group and aryl groups being optionally substituted.

4. The method according to claim 1, wherein in the boron formate having the formula (I), R.sup.1 and R.sup.2 taken together with the atom of boron to which they are bonded, form a heterocycle comprising 5 to 10 members, said heterocycle being optionally substituted.

5. The method according to claim 1, wherein in the boron formate having the formula (I), X is chosen from the group formed a halogen atom, OCHO and a sulfonate group having the formula OSO.sub.2R.sup.7, in which R.sup.7 is chosen from a methyl group (CH.sub.3), a trifluoromethyl group (CF.sub.3), a toluene group (p-CH.sub.3CH.sub.4) and a benzene group (C.sub.6H.sub.5).

6. The method according to claim 1, wherein Z is a cation chosen from the group formed by triethylammonium (HNEt.sub.3.sup.+), di-isopropylethylammonium (i-Pr.sub.2EtNH.sup.+), 2,2,6,6-tetramethylpiperidinium (TMPH.sup.+), tricyclohexylphosphonium (HPCy.sub.3.sup.+), and Na.sup.+.

7. The method according to claim 1, wherein the boron formates having the formula (I) are [Et.sub.3NH.sup.+, BCy.sub.2(OCHO).sub.2.sup.], [i-Pr.sub.2EtNH.sup.+, BCy.sub.2(OCHO).sub.2.sup.], [Et.sub.3NH.sup.+, n-Bu.sub.2B(OCHO).sub.2.sup.], [Et.sub.3NH.sup.+, BBN(OCHO).sub.2.sup.], [i-Pr.sub.2EtNH.sup.+, BBN(OCHO).sub.2.sup.], [Na.sup.+, BBN(OCHO).sub.2.sup.], [Cy.sub.3PH.sup.+, BBN(OCHO).sub.2.sup.] and [TMPH.sup.+, BBN(OCHO).sub.2.sup.].

8. The method according to claim 1, wherein it takes place in one or a mixture of at least two solvents chosen from the group formed by: the ethers chosen from diethyl ether, THF, diglyme, 1,4-dioxane; the hydrocarbons chosen from benzene, or toluene; the nitrogenous solvents chosen from pyridine, or acetonitrile; the sulfoxides chosen from dimethyl sulfoxide; the alkyl halides chosen from chloroform, or methylene chloride; and a supercritical fluid chosen from supercritical CO.sub.2.

9. The method according to claim 1, wherein the quantity of the unsaturated organic compounds to be reduced is from 0.5 to 2 molar equivalents, with respect to the boron formate having the formula (I).

10. The method according to claim 1, wherein it takes place in the presence of an additive chosen from: the crown ethers chosen from the group formed by 12-crown-4, 15-crown-5, 18-crown-6, dibenzo-18-crown-6, benzo-18-crown-6, benzo-15-crown-5, and dibenzo-15-crown-5; the aza-crowns chosen from the group formed by 1,4,7,10-tetraazacyclododecane (cyclen), 1,4,7,10,13,16-hexaazacyclooctadecane (hexacyclen), and diaza-18-crown-6; the crown thioethers chosen from the group formed by 1,5,9,13-tetrathiacyclohexadecane (16-Ane-S.sub.4), and 1,4,7,10,13,16-hexathiacyclooctadecane (18-Ane-S.sub.6).

11. The method according to claim 10, wherein the quantity of additive is from 1 to 2 molar equivalents, inclusive, with respect to the boron formate having the formula (I).

12. The method according to claim 1, wherein when n=1, the boron formate has the general formula (Ib) ##STR00007## and in that the reduction takes place in the absence of a base.

13. (canceled)

14. A method for preparing methanol, comprising (i) a step of reducing formic acid or one of its esters having the formula HCO.sub.2R.sup.8 in which R.sup.8 is chosen from a hydrogen atom, an alkyl group, and an aryl group, with a boron formate having the formula (I) according to the method of claim 1, and optionally (ii) a step of hydrolysis.

15. A method for preparing methylated amines having the formula R.sup.1R.sup.2NCH.sub.3 with R.sup.1 and R.sup.2 as defined in claim 1, comprising (i) a step of reducing formic acid in the presence of a primary amine or a secondary amine, with a boron formate having the formula (I) according to the method of claim 1, and (ii) distillation or concentration under vacuum or column chromatography.

16. A method for preparing formaldehyde, comprising a step of reducing formic acid or one of its esters having the formula HCO.sub.2R.sup.8 in which R.sup.8 in which R.sup.8 is R.sup.8 is chosen from a hydrogen atom, an alkyl group, and an aryl group, with a boron formate having the formula (I) according to the method of claim 1, and optionally (ii) a step of hydrolysis.

17. A method for preparing an alcohol having the formula R.sup.1CH.sub.2OH with R.sup.1 as defined in claim 1, comprising (i) a step of reducing an unsaturated organic compound chosen from the group formed by the aldehydes, the carboxylic acids and the esters with a boron formate having the formula (I) according to the method of claim 1, and optionally (ii) a step of hydrolysis.

Description

[0201] Other advantages and features of the present invention will be clear upon reading the examples below that are given for informational purposes and are non-limiting and the appended figures:

[0202] FIG. 1 shows details of the industrial method for preparing NaBH.sub.4 sodium tetraborohydride (TBHS) from borax, a natural source of the element boron;

[0203] FIG. 2 shows the dismutation of formic acid into CO.sub.2 and methanol;

[0204] FIG. 3 shows two reactions of decomposition of formic acid that compete with the reaction of dismutation of formic acid into methanol and CO.sub.2. These two reactions are: the dehydrogenation of formic acid into CO.sub.2 and H.sub.2 (Equation (4)) and the dehydration of formic acid into CO and H.sub.2O (Equation (5));

[0205] FIG. 4 shows examples of N-heterocyclic carbenes;

[0206] FIG. 5 shows the preparation of formic acid via electro-reduction at 2e.sup. or catalytic hydrogenation of CO.sub.2;

[0207] FIG. 6 shows the reduction of aldehydes, ketones, carboxylic acids and esters, into alcohols; imines into amines; and amides into amines or into alcohols with R.sup.1, R.sup.2, and R.sup.3 as defined above;

[0208] FIG. 7 shows an example of reduction of an aldehyde into a primary alcohol according to the method of the invention, as well as the particular case of dismutation of boron formate having the formula (I) or (Ib) into methanol, into formaldehyde and a methylated amine;

[0209] FIG. 8 shows the heterolytic cleavage of H.sub.2 with an FLP, namely (B(C.sub.6F.sub.5).sub.3+t-Bu.sub.3P), in order to form a salt, namely a phosphonium (PH.sup.+) of boratohydride (BH.sup.), followed by the hydrogenation of CO.sub.2 by said salt in order to lead to the corresponding boron formate.

EXAMPLES

[0210] A set of results is presented below, giving examples of syntheses of boron formates and of their uses in reactions of reduction of aldehydes but also of dismutation into methoxyboranes and of methylation of amines. The yields are obtained by integration of the signals of the reduced product with respect to those of mesitylene or of diphenylmethane (Ph.sub.2CH.sub.2) used as an internal standard.

[0211] In the case of the preparation of the methanol via the reaction of dismutation of the formic acid, the yields are calculated while respecting the stoichiometry of the reaction of dismutation namely that at best, 3 moles of formic acid give at most 1 mol of methanol.

[0212] Yield of reduction product:

[00001]$\left(\mathrm{reduction}\right)=\frac{n\left(\mathrm{reduced}.Math..Math.\mathrm{product}\right)}{n_0\left(\mathrm{substrate}.Math..Math.\mathrm{to}.Math..Math.\mathrm{be}.Math..Math.\mathrm{reduced}\right)}$

[0213] Yield of methanol:

[00002]$\left(\mathrm{MeOH}\right)=\frac{3n\left(\mathrm{MeOH}\right)}{n_0\left(\mathrm{HCOOZ}\right)}$

[0214] Yield of methoxyborane:

[00003]$\left({\mathrm{MeOBR}}^1.Math.R^2\right)=\frac{3n\left({\mathrm{MeOBR}}^1.Math.R^2\right)}{n_0\left(\mathrm{HCOOZ}\right)}$

[0215] Yield of methylated amine:

[00004]$\left({\mathrm{MeNR}}^1.Math.R^2\right)=\frac{n\left({\mathrm{MeNR}}^1.Math.R^2\right)}{n_0\left({\mathrm{HNR}}^1.Math.R^2\right)}$ [0216] n(reduced product): quantity of matter of reaction product determined by .sup.1H NMR with respect to mesitylene [0217] n.sub.0(substrate): quantity of matter of substrate that can be reduced initially introduced. [0218] n(MeOH): quantity of matter determined by .sup.1H NMR with respect to mesitylene. [0219] n.sub.0(MeOBR.sup.1R.sup.2): quantity of matter of methoxyborane determined by .sup.1H NMR with respect to mesitylene. [0220] n(MeNR.sup.1R.sup.2): quantity of matter of methylated amine determined by .sup.1H NMR with respect to mesitylene or diphenylmethane. [0221] n.sub.0(HNR.sup.1R.sup.2): quantity of matter of amine initially introduced in the form of free amine or as Z in the boron formates having the formula (Ib) [0222] n.sub.0(HCOOZ)=n.sub.0(HCOOH)+n.sub.0(HCOOM): total quantity of matter of formic acid (HCOOH) and its derivatives (HCOOM, M as defined above) initially introduced.

Protocol of Preparation of the Boron Formates Having the Formula (I)

[0223] The boron formate having the formula (I) can be prepared according to the following experimental protocol: [0224] 1. Under an inert atmosphere, in a glove box, the organoborane having the formula (II), the formic acid or one of its derivatives, or a mixture of formic acid and of at least one of its derivatives and optionally, the solvent and/or the base and/or the additive are introduced into a Schlenk tube that is then sealed by a J. Young valve. The order of introduction of the reactants is not important. [0225] 2. The reaction mixture is then stirred at a temperature between 0 and 30 C. (preferably at the ambient temperature, that is to say 205 C.) until the total conversion of the formic acid (from 5 minutes to 24 hours of reaction). The monitoring of the reaction is carried out via NMR of the proton .sup.1H and/or .sup.13C and/or .sup.11B. [0226] 3. When the reaction is finished (which corresponds to the appearance of the signal characteristic of boron formates in .sup.11B NMR), the solvent and the volatile compounds are evaporated under vacuum (10.sup.2 mbar). In certain cases, it is also possible to precipitate the boron formate by addition of pentane into the reaction medium, and the latter is then recovered via Bchner filtration. [0227] 4. The residue obtained after evaporation of the volatiles is then washed with pentane and ether in order to obtain a solid that is then dried under dynamic vacuum for at least 2 h.

Example 1: Synthesis of [Et.SUB.3.:NH.SUP.+., Cy.SUB.2.B(OCHO).SUB.2..SUP..] (R.SUB.1.=R.SUB.2.=Cy; X=OCHO, Z=Et.SUB.3.NH.SUP.+.)

[0228] The dicyclohexylborane Cy.sub.2BH is synthesised using a procedure described in the literature (A. Abiko, Org. Synth. 2002, 79, 103) and is then used without any particular purification.

[0229] Cy.sub.2BH (481 mg, 2.7 mmol, 1 equiv.) and 5 mL of toluene are added into a 25 mL round-bottom flask provided with a magnetic bar and a J-Young valve. The suspension obtained is stirred until total dissolution of the solid and then formic acid (204 L, 5.4 mmol, 2 equiv) is added using a syringe, followed by NEt.sub.3 (377 L, 2.7 mmol, 1 equiv) all at once. A strong release of gaseous hydrogen is observed. The reaction is then stirred for 2 h at ambient temperature and then the solvent is evaporated to dryness, leaving a very viscous oil. After multiple additions of pentane and trituration of the oil in hexane, the crystallised oil and a white solid are obtained, the latter is then recovered via filtration and washed with pentane (32 mL) and with ether (32 mL). The white solid thus recovered is dried at reduced pressure in order to obtain [Et.sub.3NH.sup.+, Cy.sub.2B(OCHO).sub.2.sup.] (901 mg) with a yield of 90%.

[0230] .sup.1H NMR (200 MHz, CD.sub.3CN) 8.77 (s, 1H, NH), 8.29 (s, 2H, HC(O)O), 3.13 (t, J=7.2 Hz, 6H), 1.65 (d, J=4.3 Hz, 4H), 1.50 (d, J=12.8 Hz, 4H), 1.24 (t, J=7.3 Hz, 9H), 1.12 (d, J=7.6 Hz, 4H), 1.01-0.73 (m, 4H), 0.48 (tt, J=12.0 Hz, 2H, CHB) ppm.

[0231] .sup.13C NMR (50 MHz, CD.sub.3CN) 166.43, 47.39, 29.38, 28.50, 9.06. ppm.

[0232] .sup.11B NMR (64 MHz, CD.sub.3CN) 11.17 ppm.

[0233] Elemental analysis: calc. (%) for C.sub.20H.sub.40BNO.sub.4 (369.30 g.Math.mol.sup.1): C, 65.04, H, 10.92, N, 3.79; found: C, 63.05, H, 11.03, N, 3.41.

Example 2: Synthesis of [Et.SUB.3.NH.SUP.+., BBN(OCHO).SUB.2..SUP..] (R.SUB.1.=R.SUB.2.=BBN; X=OCHO, Z=Et.SUB.3.NH.SUP.+.)

[0234] 9-BBN dimer (1.95 g, 7.98 mmol, 0.5 equiv.) and 20 mL of toluene are added into a 100 mL round-bottom flask provided with a magnetic bar and a J-Young valve. The suspension obtained is stirred until total dissolution of the solid and then formic acid (1.2 mL, 31.92 mmol, 2 equiv) is added using a syringe, followed by triethylamine (2.2 mL, 15.96 mmol, 1 equiv) all at once. A strong release of gaseous hydrogen is observed. The reaction is then stirred for 2 h at ambient temperature then pentane (5 mL) is added then the solvent is evaporated to dryness, leaving a very viscous oil. The oil is triturated in hexane until a solid is obtained, and the white solid obtained is then recovered via filtration and washed with pentane (34 mL) and with ether (34 mL). The white solid thus recovered is dried at reduced pressure in order to obtain [Et.sub.3NH.sup.+, BBN(OCHO).sub.2.sup.] with a yield of 92%.

[0235] .sup.1H NMR (200 MHz, CD.sub.3CN) 8.60 (bs, 1H), 8.44 (s, 2H), 3.14 (q. J=7.3 Hz, 6H), 1.88-1.36 (m, 12H), 1.24 (t, J=7.3 Hz, 9H), 0.75 (bs, 2H) ppm.

[0236] .sup.13C NMR (50 MHz, CD.sub.3CN) 167.84, 47.46, 32.09, 25.58, 9.04 ppm.

[0237] .sup.11B NMR (64 MHz, CD.sub.3CN) 8.98 ppm.

[0238] Elemental analysis: calc (%) for C.sub.16H.sub.32BNO.sub.4 (313.25 g.Math.mol.sup.1): C, 61.35, H, 10.30, N, 4.47; found: C, 58.29, H, 10.13, N, 4.28.

Example 3: Synthesis of [i-Pr.SUB.2.EtNH.SUP.+., BBN(OCHO).SUB.2..SUP..] (R.SUB.1.=R.SUB.2.=BBN; X=OCHO, Z=i-Pr.SUB.2.EtNH.SUP.+.)

[0239] Via a procedure similar to that described for [Et.sub.3NH.sup.+, BBN(OCHO).sub.2.sup.] while replacing the triethylamine with diisopropylethylamine (DIPEA), the white solid [i-Pr.sub.2EtNH.sup.+, BBN(OCHO).sub.2.sup.] is obtained with a yield of 76% (766 mg).

[0240] .sup.1H NMR (200 MHz, CD.sub.3CN) 8.44 (s, 2H), 7.87 (bs, 1H), 3.68 (h, 2H), 3.15 (q, J=7.2 Hz, 2H), 1.88-1.15 (m, 27H), 0.74 (s, 2H).

[0241] .sup.13C NMR (50 MHz, CD.sub.3CN) 167.75, 55.47, 43.61, 32.08, 25.60, 18.57, 17.26, 12.85.

[0242] .sup.11B NMR (64 MHz, CD.sub.3CN) 9.03.

[0243] Elemental analysis: calc (%) for C.sub.18H.sub.36BNO.sub.4 (341.29 g.Math.mol.sup.1): C, 63.35, H, 10.63, N, 4.10. found: C, 62.80, H, 10.67, N, 3.99.

Example 4: Synthesis of [Cy.SUB.3.PH.SUP.+., BBN(OCHO).SUB.2..SUP..] (R.SUB.1.=R.SUB.2.=BBN; X=OCHO, Z=Cy.SUB.3.PH.SUP.+.)

[0244] Via a procedure similar to that described for [Et.sub.3NH.sup.+, BBN(OCHO).sub.2.sup.] while replacing the triethylamine with tricyclohexylphosphine (Cy.sub.3P, 20% by weight in the toluene), the white solid [Cy.sub.3PH.sup.+, BBN(OCHO).sub.2.sup.] is obtained with a yield of 73% (729 mg).

[0245] .sup.1H NMR (200 MHz, CD.sub.3CN) 8.44 (s, 2H), 2.51 (q, J=11.7 Hz, 3H), 1.87-1.22 (m, 43H), 0.72 (s, 2H).

[0246] .sup.13C NMR (50 MHz, CD.sub.3CN) 166.85, 32.22, 28.88, 28.46, 28.12, 26.92, 26.66, 25.79.

[0247] .sup.11B NMR (64 MHz, CD.sub.3CN) 8.46

[0248] .sup.31P NMR (81 MHz, CD.sub.3CN) 32.21 (s).

Example 5: Synthesis of [TMPH.SUP.+., BBN(OCHO).SUB.2..SUP..] (R.SUB.1.=R.SUB.2.=BBN; X=OCHO, Z=TMPH.SUP.+.)

[0249] Via a procedure similar to that described for [Et.sub.3NH.sup.+, BBN(OCHO).sub.2.sup.] while replacing the triethylamine with 2,2,6,6-tetramethylpiperidine (TMP), the white solid [Cy.sub.3PH.sup.+, BBN(OCHO).sub.2.sup.] is obtained with a yield of 89% (890 mg). The white solid obtained is purified via recrystallisation in acetonitrile.

[0250] .sup.1H NMR (200 MHz, CD.sub.3CN) 8.44 (s, 2H), 7.87 (bs, 1H), 3.68 (h, 2H), 3.15 (q, J=7.2 Hz, 2H), 1.88-1.15 (m, 27H), 0.74 (s, 2H).

[0251] .sup.13C NMR (50 MHz, CD.sub.3CN) 169.13, 60.45, 37.22, 33.97, 29.24, 27.52, 18.51.

[0252] .sup.11B NMR (64 MHz, CD.sub.3CN) 8.30.

[0253] Elemental analysis: calc (%) for C.sub.19H.sub.36BNO.sub.4 (353.31 g.Math.mol.sup.1): C, 64.59. H, 10.27, N, 3.96. found: C, 64.15, H, 10.31, N, 4.02.

Base Protocol for the Reduction of Unsaturated Organic Compounds with the Boron Formates Having the Formula (I)

[0254] For the reduction of the organic compounds having an unsaturated function that can be reduced, the boron formates are reacted with the substrate to be reduced (if the latter is not the formic acid itself) or to be functionalised. The latter can be an organic compound having at least one unsaturated function that can be reduced: aldehydes, ketones, imines, carboxylic acids, amides, esters. It is also possible to add an amine (primary or secondary) in order to carry out the methylation of the latter when the substrate is the formic acid itself (dismutation conditions).

[0255] These reductions can be carried out according to the following protocol: [0256] 5. Under an inert atmosphere, in a glove box, the boron formate having the general formula (I) (0.01 to 2 molar equivalent with respect to the substrate), the substrate to be reduced, and optionally the formic acid and/or one of its derivatives, the solvent and/or the base and/or the additive are introduced into a Schlenk tube that is then sealed by a J. Young valve. The order of introduction of the reactants is not important. [0257] 6. The Schlenk is then heated to a temperature between 25 and 150 C. (preferably >80 C.) until total conversion of the formic acid (from 5 minutes to 48 hours of reaction). The monitoring of the reaction is carried out via NMR of the proton .sup.1H and/or .sup.13C and/or .sup.11B and/or .sup.31P. [0258] 7. When the reaction is finished (which corresponds to the disappearance of the signals characteristic of the protons of the HCOO.sup. formate in .sup.1H NMR), the pressure in the tube is released. At this stage, the treatment of the reactions depends on the nature of the reduced product obtained. The examples below allow the differences in treatment of the reduction reactions according to the products obtained to be assessed.

Example 6: Formation of Methanol

[0259] According to the general protocol presented above, an NMR tube provided with a J-Young valve is filled with [Et.sub.3NH.sup.+, BBN(OCHO).sub.2.sup.] (0.125 mmol). The latter is then dissolved in acetonitrile (0.30 mL), the tube is sealed and heated at 130 C. for 19 h. The volatile compounds (MeCN and NEt.sub.3) are then evaporated under vacuum (10.sup.1 to 10.sup.2 mbar), the viscous solid residue obtained is then dissolved in THF and H.sub.2O (5-10 equiv. with respect to the boron formate initially introduced) is added to the reaction mixture. The solution is stirred for 30 minutes to 1 hour at ambient temperature (205 C.). The volatile methanol is then recovered in another Schlenk tube via transfer at a reduced pressure. An aqueous solution of methanol is thus obtained with a yield of 49%.

[0260] The table below brings together several results allowing methanol to be obtained with various boron formates and after aqueous hydrolysis (carried out as described above).

TABLE-US-00001 Temperature Time Yield Reactant (mmol) Solvent ( C.) (h) (%) [Et.sub.3NH.sup.+,BBN(OCHO).sub.2.sup.] MeCN 130 19 49 (0.125) [Et.sub.3NH.sup.+,Cy.sub.2B(OCHO).sub.2.sup.] MeCN 120 7 31 (0.125) [i- MeCN 130 7 50 Pr.sub.2EtNH.sup.+,BBN(OCHO).sub.2.sup.] [Na.sup.+,BBN(OCHO).sub.2.sup.] + MeCN 130 24 58 15-C-5

Example 7: Formation of Methylated Amines

[0261] According to the general protocol presented above, an NMR tube provided with a J-Young valve is filled with [TMPH.sup.+, BBN(OCHO).sub.2.sup.] (0.125 mmol). The latter is then dissolved in acetonitrile (0.30 mL), the tube is sealed and heated at 130 C. for 23 h. The volatile compounds are then transferred under vacuum (10.sup.1 to 10.sup.2 mbar) into another Schlenk tube. A solution consisting of TMP and of TMP-CH.sub.3 (methylated TMP, 23% yield) in acetonitrile is thus obtained. The latter can be separated via distillation at a reduced pressure (T.sub.eb (760 mmHg or 1.0132472 bar)=152 C. and 187 C., respectively). It should be noted that the TMP regenerated at the end of the reaction can be reused in order to form [TMPH.sup.+, BBN(OCHO).sub.2.sup.] via the method of the invention.

Example 8: Formation of Formaldehyde

[0262] According to the general protocol presented above, an NMR tube provided with a J-Young valve is filled with [Cy.sub.3PH.sup.+, BBN(OCHO).sub.2.sup.] (0.125 mmol). The latter is then dissolved in acetonitrile (0.30 mL), the tube is sealed and heated at 130 C. for 5.5 h. At this stage, the formaldehyde is obtained selectively (methanol is not observed) in the form of the acetal Cy.sub.3PCH.sub.2OBBN(OCHO). The volatile compounds are then transferred under vacuum (10.sup.1 to 10.sup.2 mbar) into another Schlenk tube and the solid residue obtained is then dissolved in THF and H.sub.2O (5-10 equiv. with respect to the boron formate initially introduced) is added to the reaction mixture. The solution is stirred for 30 minutes to 1 hour at ambient temperature (205 C.). An aqueous solution of formaldehyde (28% yield) that must be used as such if needed is thus obtained.

Example 9: Reduction of Benzaldehyde into Benzyl Alcohol

[0263] According to the general protocol presented above, an NMR tube provided with a J-Young valve is filled with [EtNH.sup.+, BBN(OCHO).sub.2.sup.] (0.10 mmol), benzaldehyde (0.05 mmol) and acetonitrile (0.30 mL), the tube is sealed and heated at 130 C. for 5 h. The volatile compounds (MeCN and NEt.sub.3) are then evaporated under vacuum (10.sup.1 to 10.sup.2 mbar), the viscous solid residue obtained is then dissolved in THF and H.sub.2O (5-10 equiv. with respect to the boron formate initially introduced) is added to the reaction mixture. The solution is stirred for 30 minutes to 1 hour at ambient temperature (205 C.). The benzyl alcohol formed is then recovered via transfer at a reduced pressure into another Schlenk tube. A solution of benzyl alcohol is thus obtained with a yield of 99%. The latter can finally be recovered and purified via distillation (T.sub.eb (760 mmHg or 1.0132472 bar)=203 C.).

Example 10: Reduction of Cinnamaldehyde into Cinnamic Alcohol

[0264] According to the general protocol presented above, an NMR tube provided with a J-Young valve is filled with [Et.sub.3NH.sup.+, BBN(OCHO).sub.2.sup.] (0.10 mmol), cinnamaldehyde (0.05 mmol) and acetonitrile (0.30 mL), the tube is sealed and heated at 130 C. for 5 h. The volatile compounds (MeCN and NEt.sub.3) are then evaporated under vacuum (10.sup.1 to 10.sup.2 mbar), the viscous solid residue obtained is then dissolved in THF and H.sub.2O (5-10 equivalents with respect to the boron formate initially introduced) is added to the reaction mixture. The solution is stirred for 30 minutes to 1 hour at ambient temperature (205 C.). The cinnamic alcohol formed (yield of 80%) can finally be recovered and purified via distillation (T.sub.eb(760 mmHg or 1.0132472 bar)=250 C.).

Example 11: Reduction of 4-Chlorobenzaldehyde into 4-Chlorobenzyl Alcohol

[0265] According to the general protocol presented above, an NMR tube provided with a J-Young valve is filled with [Et.sub.3NH.sup.+, BBN(OCHO).sub.2.sup.] (0.10 mmol), 4-chlorobenzaldehyde (0.05 mmol) and acetonitrile (0.30 mL), the tube is sealed and heated at 130 C. for 5 hours. The volatile compounds (MeCN and NEt.sub.3) are then evaporated under vacuum (10.sup.1 to 10.sup.2 mbar), the viscous solid residue obtained is then dissolved in THF and H.sub.2O (5-10 equivalents with respect to the boron formate initially introduced) is added to the reaction mixture. The solution is stirred for 30 minutes to 1 hour at ambient temperature (20=5 C.). The alcohol 4-chlorobenzyl alcohol formed (yield of 99%) can finally be recovered and purified via distillation (T.sub.eb(760 mmHg or 1.0132472 bar)=234 C.).

Observation:

[0266] It should be noted that the reactions leading to the methylated amines or to formaldehyde only form the latter as reduction products. In other words, the average yields observed for these reactions can be corrected by taking into account the fact that the other products are the starting products (amine of formate) or the gases CO.sub.2 and H.sub.2. In all cases, the latter can be reused in the method in order to prepare the formic acid or the boron formate having the formula (I).