Stereospecific Synthesis of Alkenes by Eliminative Cross-Coupling of Enantioenriched sp<sup>3</sup>
-Hybridized Carbenoids
作者:Zhenhua Wu、Xun Sun、Kristin Potter、Yang Cao、Lev N. Zakharov、Paul R. Blakemore
DOI:10.1002/anie.201606641
日期:2016.9.26
1‐Aryl‐1,2‐dialkylethenes were generated by a sequence of electrophilic substitution, 1,2‐metalate rearrangement, and β‐elimination initiated by the addition of enantioenriched α‐(carbamoyloxy)alkylboronates to enantioenriched lithiated carbamates. The carbenoid stereochemical pairing [i.e., “like”=(S)+(S) or “unlike”=(S)+(R)] and the elimination mechanism (syn or anti), not substituent effects, determined
1-芳基1,2-二烷基乙烯是通过一系列亲电取代,1,2-金属盐重排以及通过将对映体富集的α-(氨基甲酰氧基)烷基硼酸酯添加到对映体富集的锂化氨基甲酸酯中而引发的β-消除。所述卡宾立体化学配对[即,“像” =(小号)+(小号)或“不同于” =(小号)+([R)〕和消除机构(顺式或反),而不是取代基的影响,确定的配置三取代烯烃目标。例如,(Z)-2,5-二苯基-2-戊烯的产率为70%,其中E / Z = 5:95类似于Li和B的类胡萝卜素的结合以及顺式(热)消除,而E 异构体的收率相同,E / Z > 98:2,是通过其他相同的方法进行的,涉及立体化学配对不同。详细阐述的概念克服了直接连接烯烃合成的传统策略的固有局限性,除非将烯烃取代基进行强烈区分,否则传统策略无法实现有意义的立体化学偏向。