Highly Diastereoselective Synthesis of Methylenecyclobutanes by Merging Boron-Homologation and Boron-Allylation Strategies.

A highly diastereoselective synthesis of methylene-cyclobutanes possessing a quaternary stereocenter is reported, in which boron homologation of an easily-generated cyclobutenylmetal species is performed, followed by an allylation reaction. Combining three steps in a one-pot process further optimized the method, which afforded the expected adducts in excellent yields and stereoselectivity, starting from commercially available 4-bromobutyne. [ABSTRACT FROM AUTHOR]