Double metal catalyst constructs 5-carbon rings

Abstract

Creating rings, or carbocycles, with a six-carbon skeleton is an elementary exercise for synthetic organic chemists. Ask one how it’s done, and the chemist will inevitably point to the stalwart Diels-Alder reaction, which weds a 1,3-diene with a dienophile in an elegant [4 + 2] cycloaddition. But there’s been no analogous method for making five-carbon rings—until now. Purdue University chemists Christopher Uyeda and You-Yun Zhou report a new [4 + 1] cycloaddition that constructs cyclopentenes from a 1,3-diene and a highly reactive vinylidene (Science 2019, DOI: 10.1126/science.aau0364). “This reaction allows you to access five-membered rings in a very expedient way. That’s been challenging for a long time in cycloaddition chemistry,” Uyeda says. The key component of the reaction is a dinickel catalyst in which the two metal atoms sit side by side. This catalyst helps form a reactive vinylidene from a 1,1-dichloroalkene and then guides the vinylidene to react with