A Practical Solution to Stereodefined Tetrasubstituted Olefins

作者：Dai, Jianxin; Wang, Minyan; Chai, Guobi; Fu, Chunling; Ma, Shengming^*

来源：Journal of the American Chemical Society, 2016, 138(8): 2532-2535.

DOI：10.1021/jacs.6b00051

• STEREOSELECTIVE CONJUGATE ADDITION
• ALPHA,BETA-UNSATURATED ESTERS
• BETA,GAMMA-UNSATURATED ESTERS
• ENANTIOSELECTIVE PROTONATION
• GRIGNARD-REAGENTS
• SAMARIUM DIIODIDE
• CARBOXYLIC-ACIDS
• EFFICIENT
• 2,3-ALLENOATES
• DERIVATIVES

Olefins, compounds with a carbon-carbon double bond, are of fundamental importance, and stereodefined construction of tetrasubstituted carbon-carbon double bond is a significant challenge. Here we show a unique and practical method for the preparation of stereodefined, fully substituted olefins via conjugate addition of organozinc reagents to readily available 2,3-allenals. Through mechanistic studies, it is confirmed that the geometry of the newly formed double bond is controlled by unique regiospecific oxygen-protonation of the enolate intermediates, generating 1,3-alkadienols. Such alkadienols would undergo a concerted 1,5-H-transfer reaction via a six-membered transition state to ensure the configuration of the carbon-carbon double bond in the final products. Using the readily available organozinc reagents and 2,3-allenals provides a very rapid access to a wide range of tetrasubstituted olefins with defined stereochemistry, bearing an extremely versatile aldehyde functionality.

• 出版日期2016-3-2
• 单位浙江大学