Division of Applied Chemistry, Graduate School of Natural Science and Technology, and ‡Research Institute for Interdisciplinary Science, Okayama University , 3-1-1 Tsushimanaka, Kita-ku, Okayama 700-8530, Japan.
J Am Chem Soc. 2017 Sep 20;139(37):13184-13192. doi: 10.1021/jacs.7b07487. Epub 2017 Sep 5.
Stabilization by a silyl group on the methylene carbon and a diamine ligand led to the isolation of gem-dichromiomethane species. X-ray crystallography confirmed the identity of the structure of this rare example of reactive gem-dimetalloalkane species. The isolated gem-dichromiomethane complex acted as a storable silylmethylidene carbene equivalent, with reactivity that could be changed dramatically upon addition of a Lewis acid (ZnCl) and a base (TMEDA) to promote both silylalkylidenation of polar aldehydes and silylcyclopropanation of nonpolar alkenes. Identification of a key reactive species also identified the catalytic version of these transformations and provided insights into the reaction mechanism. In contrast to Simmons-Smith cyclopropanation, the real reactive species for the current cyclopropanation was a chromiocarbene species, not a chromium carbenoid species.
硅基和二胺配体稳定亚甲基碳原子，从而分离出偕二铬甲烷物种。X 射线晶体学证实了这种罕见的反应性偕二金属烷烃物种的结构。分离出的偕二铬甲烷配合物作为可储存的亚甲硅烷基卡宾等价物，其反应性在加入路易斯酸（ZnCl）和碱（TMEDA）后可显著改变，以促进极性醛的硅烷基烯丙基化和非极性烯烃的硅烷基环丙烷化。关键反应性物种的鉴定也确定了这些转化的催化形式，并提供了对反应机制的深入了解。与 Simmons-Smith 环丙烷化反应相反，当前环丙烷化反应的真正活性物种是铬卡宾物种，而不是铬碳烯物种。
