Methyl sulfide, complex with

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. 

Borane- dimethyl sulfide complex Methyl sulfide, compd. with borane (1 1) Borane, compd. with thiobis[methane] (1 1) (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... 

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. 

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. 

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. 

The Step 4 product (8 mmol) dissolved in 20 ml THF at 0°C was treated with 16 ml 2M borane-methyl sulfide complex in THF, then stirred 20 hours, and quenched with methyl alcohol. The mixture was concentrated, the residue purified as in Step 4, and the product isolated in 70% yield as a colorless oil. 

Dichloroborane and monochloroborane etherates or their methyl sulfide complexes have been prepared by the reaction of borane and boron trichloride [44]. The hydroboration of alkenes with these borane reagents is, however, usually very slow because of the slow dissociation of the complex. Dichloroborane prepared in pentane from BCI3 and trimethylsilane is unusually highly reactive with alkenes and alkynes hydroboration is instantaneous at -78 °C (Eq. 20) [45]. 

For the synthesis of trialkylboranes. hydroboration is carried out with a borane solution in THF or with the borane-methyl sulfide complex (BMS) in THF, diethyl ether, or dichloromethane. Diborane reacts rapidly and quantitatively with alkenes to produce a solution of trialkylborane [16] (eq (13)). The addition of dialkylboranes. such as 9-borabicyclo[3.3.1]nonane (9-BBN. 3). disiamylborane (1), or dicyclohexylb-orane (2), to alkenes or alkynes gives mixed alkylboron compounds. The high regio-. stereo-, or chemoselectivity in the additions of these borane reagents unsaturated C—C bonds have been extensively used in organic syntheses. 

The 1-alkenylboronic acids are also obtained by hydroboration of alkynes with diboroborane-methyl sulfide complex followed by hydrolysis [21] Dihydroboration of terminal alkyne with two equivalent of 9-BBN followed by dehydroboration with ben-zaldehyde stereoselectively provides 9-[(E)-l-alkenyl]-9- BBN in high yields [56]. 

The B-Br bond can be conveniently converted to the corresponding isopropyl esters with diisopropyl ether, However, the reaction with the corresponding methyl sulfide complex is very slow. 

Hydroboration of divinyldimethylsilane (123) with borane-methyl sulfide complex (BMS), followed by methanolysis affords a 7 1 ratio of the silaborolane (124) and silaborinane (125) in 47% yield (Scheme 13) <84JOC2565>. Upon treatment with tert-butyllithium, the corresponding tert-butyl boracycles (126) and (127), respectively, were obtained in 60% yield. 

Malate esters are easily reduced in a highly selective fashion using either diborane [40,41] or borane—methyl sulfide complex [42— 45] in the presence of a catalytic amount of sodium borohydride (5 mol%) to give diol esters 45. Yields of 45a and 45b generally range from 80-97%, while 45c is formed in 60% yield [46]. Dimethyl (5)-malate is reduced with 99 1 selectivity as regards C-1 to C-4 ester reduction, while diethyl ( S)-malate shows even greater selectivity (200 1). 

A solution of 10 mL of borane-methyl sulfide complex (10 M BH3 in methyl sulfide) in 75 mL THF was placed in a He atmosphere, cooled to 0 °C, treated with 21 mL of 2-methylbutene, and stirred for 1 h while returning to room temperature. This was added directly to the crude 4-... 

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