Room temperature and highly enantioselective additions of alkyltitanium reagents to aldehydes catalyzed by a titanium catalyst of (R)-h8-binol
作者:Qinghan Li、Han-Mou Gau
DOI:10.1002/chir.21018
日期:2011.11
n‐butyl as compared with the enantioselectivities of products from the addition reactions of the branched i‐butyl group. The same stereochemistry of RTi(O‐i‐Pr)3 addition reactions as the addition reactions of organozinc, organoaluminum, Grignard, or organolithium reagents directly supports the argument of that titanium‐catalyzed addition reactions of aldehydes involve an addition of an organotitanium nucleophile
制备了三种RTi(O‐ i‐ Pr)3烷基钛试剂(R = Cy(1a),i‐ Bu(1b)和n‐ Bu(1c))。高分辨率质谱表明,气相中的1b和1c是单体物种。但是,1a的固态显示出二聚体结构。(R)‐H 8的钛催化剂催化的醛中不对称地添加1a,1b,1c‐BINOL在室温下研究。该反应以良好的产率产生所需的仲醇,具有高达94%ee的良好至优异的对映选择性。本文描述了以R亲核试剂的空间体积而言的反应性和对映选择性差异。次级的加成反应Ç -己基醛比初级的反应较慢我丁基或ñ丁基亲核体。对于伯烷基,被用于从线性的加成反应产物获得下对映选择性Ñ丁基作为具有产品从支化的加成反应的对映选择性相比我丁基团。RTi(O‐ i的相同立体化学‐Pr)3加成反应作为有机锌,有机铝,格氏试剂或有机锂试剂的加成反应直接支持了这样一种论点,即钛催化醛的加成反应涉及有机钛亲核试剂的加成。手性,2011年。©2011 Wiley‐Liss,Inc