Sodium borohydride-trimethylsilyl chloride

Optically active P-hydroxysulfoximines which catalyze the asymmetric borane reduction of ketones [110], also catalyze the same reaction with sodium borohydride/trimethylsilyl chloride system as reducing agent [126]. Reduction of a protected a-hydroxyacetophenone afforded the alcohol with 90% ee. 

Enamines have been prepared through reductive-trimethylsilylation of cyanohydrins as precursors of acylsilanes.la 192 As indicated above, these enamines are also excellent starting materials for synthesizing RSMAs via reduction of the corresponding iminium chlorides with sodium borohydride.la,lb... 

To a 0 °C solution of lithium borohydride (1.32 g, 60.54 mmol) in THF (30 mL) was added trimethylsilyl chloride (15.40 mL, 121.1 mmol). The ice-water bath was removed, and the mixture was stirred at room temperature for 15 min. The mixture was cooled to 0 °C and (5)-phenylalanine (5.00 g, 30.27 mmol) was added. The ice-water bath was removed, and the reaction mixture was stirred for 16 h. The mixture was cooled again to 0 °C and methanol (45 mL) was added dropwise followed by a sodium hydroxide solution (2.5 M, 25 mL). The organic solvents were evaporated in vacuo and the residue was extracted with CHCI3 (5 x 50 mL). The combined extracts were dried (Na2SO4), filtered, and evaporated in vacuo to leave 4.55 g (99%) of (5)-phenylalaninol as a white crystalline solid. 

Since utilization of the ketone carbonyl was now complete, its removal was implemented via an efficient three-step sequence involving reductive cleavage of the derived selenocarbonate with tris(trimethylsilyl)silane [12] under free radical conditions [13]. With the acquisition of 17 in this manner, the serviceability of the reagent produced by adding sodium borohydride to cobaltous chloride for chemoselective reduction of the nitrile group [14] was assessed. Indeed, treatment of 17 in this manner, followed directly by basification with potassium hydroxide in methanol, secured 18. In this step as well as in the subsequent progression to the N-methyl derivative 19, no epimerization was seen within ring A. 

Hydrogenation and Deoxygenation. Nickel boride, produced in situ by the action of sodium borohydride on nickel(II) chloride, has been used to carry out a two-step hydrogenolysis of allylic alcohols via reductive cleavage of the trimethylsilyl ethers. Tertiary alcohols may be deoxygenated in reasonable yields by means... 

A rather similar method based on reductive alkylation of urea involves the use of trimethylsilyl chloride (TMSCl) as the catalyst in the condensation step and again utilizes sodium borohydride as the reducing agent [792]. Under these conditions, the parent urea can be converted into monosubstituted as well as disubstituted ureas in yields of 60-92%. 

Methoxy(aryl)carbene]iron complexes are obtained by reaction of the appropriate benzoic chlorides with [Fe(C5Mes)(CO)2]K to give the acyliron complexes, followed by methylation with methyl mesylate. Reduction with sodium borohydride and removal of the methoxy group by treatment with trimethylsilyl triflate affords the defunctionalized (arylcarbene)iron complexes. The presence of ortAo-methoxy or ortho-chloro substituents at the arene moiety gives rise to (T) -C,OMe) or (T1 -C,C1) chelate (arylcarbene)iron complexes upon irradiation. Disodium tetracarbonylferrate reacts with aromatic (V,A -diallylamides followed by treatment with trimethylsilyl chloride with direct formation of chelated a-aminocarbene complexes (Scheme 4-59). ... 

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