Chemoselective Reactions of (<i>E</i>)-1,3-Dienes: Cobalt-Mediated Isomerization to (<i>Z</i>)-1,3-Dienes and Reactions with Ethylene
作者:Yam N. Timsina、Souvagya Biswas、T. V. RajanBabu
DOI:10.1021/ja501979g
日期:2014.4.30
In the asymmetric hydrovinylation (HV) of an E/Z-mixture of a prototypical 1,3-diene with (S,S)-(DIOP)CoCl2 or (S,S)-(BDPP)CoCl2 catalyst in the presence of Me3Al, the (E)-isomer reacts significantly faster, leaving behind the Z-isomer intact at the end of the reaction. The presumed [LCo–H]+-intermediate, especially when L is a large-bite angle ligand, similar to DIOP and BDPP, promote an unusual isomerization
在 Me3Al 存在下,原型 1,3-二烯与 (S,S)-(DIOP)CoCl2 或 (S,S)-(BDPP)CoCl2 催化剂的 E/Z 混合物的不对称加氢乙烯基化 (HV) ,(E)-异构体反应明显更快,在反应结束时留下完整的 Z-异构体。假定的 [LCo–H]+-中间体,特别是当 L 是大咬角配体时,类似于 DIOP 和 BDPP,促进 1,3-二烯的 (E/Z)-混合物异常异构化为异构纯 Z -异构体。该反应提出了一种机制,包括通过 [η4-(二烯)(LCo-H)]+ 络合物进行分子内氢化物加成,然后是中间体 Co(烯丙基) 物质的 π-σ-π 异构化。