Reduction of α-trialkylsiloxy nitriles with diisobutylaluminium hydride (DIBAH): A facile preparation of α-trialkylsiloxy aldehydes and their derivatives
✍ Scribed by Masahiko Hayashi; Tomoko Yoshiga; Kanako Nakatani; Kazuyuki Ono; Nobuki Oguni
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- French
- Weight
- 646 KB
- Volume
- 50
- Category
- Article
- ISSN
- 0040-4020
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✦ Synopsis
The stepwise synthesis of a-trimethylsiloxy aldehydes and a-hydroxy aldehydes could be achieved via the reduction of a-trimethylsiloxy nitriles with diisobutylaluminium hydride (DIBAH) starting from a variety of ketones. The facile synthesis of optically active a-tert-butyldimethylsiloxy aldehydes was attained by combination of asymmetric silylcyanation of aldehydes and DIBAH reduction of optically active a-siloxy nitriles. Furthermore, in the reduction of some a-tert-butyldimethylsiloxy-B,y-unsaturated nitriles, migration of the double bond took place to form more stable asiloxy-a&unsaturated aldehydes under some reaction conditions. M. HAYASHI et al. butyldimethylsiloxy nitriles with DIBAH, which provides chiral a-siloxy aldehydes. The migration of the double bond in the reaction of some a-tert-butyldimethylsiloxy-p,y-unsaturated nitriles to the corresponding aidehydes will also be disclosed. Results and Discussion Stepwise Synthesis of a-Trimethylsiloxy Aldehydes and a-Hydroxy Aldehydes from Ketones. The conversion process from a-trimethylsiloxy nitriles to a-trimethylsiloxy aldehydes consists of two steps. The first step is the reduction of a-trimethylsiloxy nitriles to the corresponding imines by DIBAH, and the second step is the intermediate hydrolysis of formed a-siloxy imines to a-siloxy aldehydes by treatment with aqueous acid solution. DIBAH (1.5-2 equiv. per substrate.) was added to a hexane solution of a-trimethylsiloxy nitriles @a-2d) at -45 "C and the starting materials were consumed completely after stirring at 0 'C for 1 h in all cases. Then the reaction mixture was poured into a mixture of ether and saturated aqueous ammonium chloride solution. Treating with sulfuric acid solution under stirring vigorously at room tempera-0 cat. Znl, R' J.