Imines cyanotrimethylsilane

A-chlorosuccinimide provides (3 S, 4 S)-3,4-bis(TBSO)-l-chloropyrrolidine (771). Dehydrochlorination with DBU in benzene affords a cyclic imine that reacts with cyanotrimethylsilane in the presence of catalytic zinc iodide to afford an epimeric mixture of aminonitriles. Acidic hydrolysis of the nitrile, esterification of the resulting acid, Cbz-protection of the basic amine, and chromatographic separation affords 772 in 28% yield and 774 in 42% yield. These are converted respectively to either (25, 35,45)-3,4-dihydroxyproline (773) or (2R,3>S,4S)-3,4-dihydroxyproline (775) [230] (Scheme 169). 

Scheme 7.19 Enantioselective addition of cyanotrimethylsilane to imines using 27 and 28.

Addition to Carbonyls, Imines (Strecker-type Reactions), and Heteroaromatic Rings (Reissert-type Reactions). Cyanohydrin trimethylsilyl ethers are of significant synthetic interest as they can be transformed into a variety of multifunctional intermediates. Aldehydes and ketones can be enantioselectively converted to cyanohydrin trimethylsilyl ethers when treated with cyanotrimethylsilane in the presence of a Lewis acid and a chiral ligand. Enantioselective and/or diastereoselective formation of cyanohydrins and their derivatives has been reported and most of these reactions involve chiral ligands and metal catalysts containing Ti (eq 24), Sm (eq 25), and A1 (eq 26). ... 

Excellent enantioselectivity has also been achieved in the reaction between imines and cyanotrimethylsilane, which provides an effective synthesis of chiral a-amino acids. Ti-catalyzed reactions using a chiral tripeptide Schiff base have been developed to realize such transformations (eq 30). In addition, a combination of 2,2 -biphenol and Cinchonine as chiral ligands has been employed to effect such reactions (eq 31). An enantioselective route was also developed for the conversion of readily prepared... 

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