Opening of Tartrate Acetals Using Dialkylboron Bromide: Evidence for Stereoselectivity Downstream from Ring Fission.

✍ Scribed by William W. Ogilvie; et al. et al.

• Book ID: 101941140
• Publisher: John Wiley and Sons
• Year: 2003
• Weight: 33 KB
• Volume: 34
• Category: Article
• ISSN: 0931-7597
• DOI: 10.1002/chin.200322113

✦ Synopsis

Opening of Tartrate Acetals Using Dialkylboron Bromide: Evidence for Stereoselectivity Downstream from Ring Fission. -The opening of acetals derived from tartaric esters and amides using Br-BMe2 as Lewis acid and R2Cu(CN)Li2 as alkylating agent is a useful method to prepare chiral secondary alcohols. Good selectivity is only observed when a particular set of experimental conditions (temperature) is respected, following the opening of acetal. The diastereoselectivity originates from equilibration of bromo ether intermediates formed during acetal opening and can be improved by cuprate displacement at -30°C. At -30°C the (R)-and (S)-isomers behave differently. Additionally, it is shown that the nature and configuration of acetal substituents play an important role for the diastereoselectivity. -(