Spotlights on Recent JACS Publications

摘要

A unique driving force for reactions involving cyclical molecules is ring strain, which can be used to build otherwise challenging structures such as functionalized bicyclopentanes, cyclobutanes, and azetidines. In recent years, functionalization by strained systems relied primarily on their inherent electrophilic reactivity. Now, researchers led by Dorota Gryko harness the strain system of bicyclo[1.1.0]butanes (BCBs) to generate nucleophilic radicals via a cobalt catalytic system (DOI: 10.1021/jacs.0c00245). The cobalt catalytic system they use is based on vitamin B12, which is a cofactor for enzymes that can catalyze many different thermodynamically challenging reactions both in nature and in organic synthesis. While vitamin B12 chemistry has primarily been in the realm of S_N2-type reactions, its catalytic potential can be extended to other forms of nucleophilic transformations. The authors used a hydrophobic vitamin B12 derivative for the polarity-reversal generation of cyclobutyl radical species from electron-deficient BCBs. The formed radical species were then successfully coupled under mild conditions with electron-deficient alkenes and aryl iodides. These results show a new application for strain-release functionalization and can motivate development of other radical transformations of electrophilic bicyclic molecules. Dalia Yablon Ph.D.