Borane-methyl sulfide

Borane-methyl sulfide complex (neat) was purchased from Aldrich Chemical Company, Inc. and was used as received. 

The ligand (191.4 mg) was placed in a 100 mL round-bottomed flask equipped with a magnetic stirrer bar in an oil-bath at 40 °C, under nitrogen. Dry tetrahydofuran (66 mL) was then added. After the solution turned clear, borane-methyl sulfide complex (1.32mL) was added dropwise. The mixture was stirred at this temperature for 2.5 hours. 

Stereoselective reduction of some triazolodiazines (derivatives of ring systems 33 and 37) bearing chiral terpene residues has been elaborated by Groselj el al. <2006TA79>. With catalytic hydrogenation, partial saturation of the six-membered ring was experienced, while reaction with borane-methyl sulfide resulted in formation of triazole-boron complexes. 

Borane-methyl sulfide Borane, compound with methyl sulfide (1 1) (8) Borane, compound with thiobismethane (11) (9) (13292-87-0)... 

To verify the regiochemistry of the alkylation described above we reduced MFA with borane-methyl sulfide complex to provide 72 in 40% yield [Fig. (21)]. This compound was identical to the one prepared from the catechol 66 and 4-bromo-2-methyl-2-butene (73) using the chemistry reported in step 1 of Fig. (20), thereby conforming the assigned regiochemistry of compounds 68a-d. 

A solution of 6.0 mL of borane-methyl sulfide complex (10M BH3 in methyl sulfide) in 45 mL THF was placed in a He atmosphere, cooled to 0 °C, treated with 12.6 g of 2-methylbutene, and stirred for 1 h while returning to room temperature. To this there was added a solution of the impure 3,4-diethoxy-5-methylthiostyrene in 25 mL THF. This was stirred for 1 h during which time the color deepened to a dark yellow. The excess borane was destroyed with about 2 mL MeOH (all this still in the absence of air). There was then added 11.4 g elemental iodine followed by a solution of 2.4 g NaOH in 30 mL of boiling MeOH, added over the course of 10... 

A solution of 2 mL of borane-methyl sulfide complex (10M BH, in methyl... 

The reaction of 154 with chloroacetonitrile in the presence of potassium /-butoxide afforded 155. The nitrile group was reduced with borane methyl sulfide to the corresponding amine 156, which on treatment with sodium methoxide was transformed into the 1,4-oxazepine 157 (Scheme 23) <1996JOC6060>. 

Borane-methyl sulfide complex (68 ml, 0.71 mol) was added dropwise to a solution of (S)-(+)-mandelic acid (98.5 g, 0.65 mol) in THF (900 ml) at room temperature (RT) under a flow of argon over 3 h. The reaction was stirred for 6 h. Then methanol was added dropwise and stirring continued for a further 13 h. The volatiles were then removed in vacuum, the residue stirred in methanol, and the process repeated 3 times. Column chromatography (MeOH-ethyl acetate-petrol, gradient elution) of the residue afforded the diol (57.3 g, 64%). p-Toluenesulphonyl chloride (80 g, 98% 0.41 mol) was then added portionwise to a solution of the diol in pyridine (700 ml) at 0°C over 8 h. The reaction was stirred at RT for 13 h, then the volatiles removed in vacuum. 

Charge the flame dried and argon flushed three-necked flask with 1-octene. Cool to 0°C, add triethylborane, and slowly the borane-methyl sulfide complex. 

Charge one flame dried and argon flushed two-necked flask with triethylborane and add borane-methyl sulfide complex at rt. Dilute with ether (1 mL). The stock solution of diethylborane is now ready for use. 

Borane-methyl sulfide complex (FW76), 11.4 g, 150 mmol... 

Cool to 0°C and add the borane-methyl sulfide complex. Warm to rt and stir for 2 h. 

Borane-methyl sulfide complex, 1 molar in CH2CI2,6 ml, 6 mmol. DryTHF... 

Charge the first flame dried and argon flushed two-necked flask with (1S)-(-)-p-pinene and cool to -10°C. Add borane-methyl sulfide complex. After 10 min a thick precipitate will form. Dissolve in ether (15 mL) and stir at 0°C for 2 h. 

Charge ( )-1-(triisopropylsiloxy)-1,3-butadiene into the reaction vessel, then add diethylborane, prepared from triethylborane and borane-methyl sulfide complex, at 0°C over 10 min. 

The CBS reduction has also proven to be an efficient method for asymmetric reduction of a,ft-unsaturated enones14 and ynones15 (Scheme 4.31). The asymmetric reduction of alkynyl ketones affords propargylic alcohols 30 with high levels of enantioselectivity and in moderate to good yields. Optimized reaction conditions for the reduction are the use of THF at — 30° C, 2 equivalents of chiral oxazaborolidine 28b, and 5 equivalents of borane methyl sulfide complex. 

Commercially available solutions of H3B-THF in THF (Aldrich-Boranes, Inc., 2371 N. 30th St., Milwaukee, WI 53210) which are used in this synthesis, contain approximately 5% of sodium tetrahydroboratefl —) as a stabilizer. Tri(sec-butyl)borane prepared from these solutions should be distilled. An alternative commercial (Aldrich-Boranes, Inc.) hydroborating agent free of sodium tetrahydroborate(l —) is borane-methyl sulfide. 

Lane CF, Myatt HL, Daniels J, Hopps HB (1974) Organic synthesis using borane-methyl sulfide II Reduction of aromatic carboxylic acids in the presence of tnmethyl borate J Org Chem 39 3052-3054... 

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