Stereospecific Synthesis of Cyclobutylboronates through Copper(I)-Catalyzed Reaction of Homoallylic Sulfonates and a Diboron Derivative

摘要

Cyclobutanes have received considerable attention as prevalentnstructures in natural products and as versatile synthetic inter-nmediates.n1nHowever, synthetic methods for cyclobutanes withnmultiple stereocenters are relatively less developed than thosenfor other ring systems. [2 2] Photocycloadditions are the mostnwidely used and reliable method for stereoselective cyclobutanensynthesis; however, high regio- and stereoselectivity is almostnlimited to the enone alkene reactions.n1nCyclobutylboronatesnwith stereodefined structures are expected to be a promisingnsynthetic intermediate because they have high configurationalnstability and many stereospecific transformations of C B bondsnexist. However, highly general methods for the stereoselectivensynthesis of such compounds have been scarcely reported.n2nHerein, we describe a novel catalytic protocol for accessing cis-nand trans-1-silyl-2-borylcyclobutanes as well as 1-aryl-2-boryl-ncyclobutanes. The synthetic utility of the compounds is alsondemonstrated by their stereospecific derivatization.