Reynolds Troy E, Bharadwaj Ashwin R, Scheidt Karl A
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
J Am Chem Soc. 2006 Dec 6;128(48):15382-3. doi: 10.1021/ja0653674.
Silyloxyallenes derived from alpha-hydroxypropargylsilanes undergo efficient addition to aldehydes with catalytic amounts of Lewis acids. The allenes are accessed from the corresponding propargylsilanes in a base-catalyzed 1,2-Brook rearrangement/SE2' process. Enantioenriched propargylsilanes are synthesized by a new zinc-promoted addition of alkynes to acylsilanes in up to 74% ee. This work demonstrates that conversion to the silyloxyallenes occurs with minimal erosion in optical activity. The use of a chiral chromium(III) Lewis acid effects the catalytic asymmetric addition of racemic silyloxyallenes to aromatic aldehydes in up to 92% ee. The overall reaction is broad in scope and accommodates a wide variety of aromatic and aliphatic substituents on both the propargylsilane and aldehyde.
源自α-羟基炔丙基硅烷的甲硅烷氧基丙二烯在催化量的路易斯酸存在下能有效地与醛发生加成反应。这些丙二烯可通过相应的炔丙基硅烷在碱催化的1,2-布鲁克重排/SE2'过程中制得。对映体富集的炔丙基硅烷通过一种新的锌促进的炔烃与酰基硅烷的加成反应合成，对映体过量最高可达74%。这项工作表明，转化为甲硅烷氧基丙二烯时，光学活性的损失最小。使用手性铬(III)路易斯酸可实现外消旋甲硅烷氧基丙二烯与芳香醛的催化不对称加成反应，对映体过量最高可达92%。该反应的适用范围广泛，炔丙基硅烷和醛上的各种芳香族和脂肪族取代基均可适用。
