Regio- and Diastereoselective Highly Strained Alkylidenecyclobutane Isomerization/Hydroacylation: Synthesis of Multisubstituted Cyclobutanes with Consecutive Stereocenters

The regio- and diastereoselective alkene isomerization and hydrofunctionalization sequence enabled by transition-metal complexes allows rapid activation and assembly of the C(sp³)–H bond that is either adjacent or distal to the initial double bond, which has been a longstanding challenge in this field. Herein, we develop unusual rhodium-catalyzed isomerization of alkylidenecyclobutanes with subsequent hydroacylation reaction to provide multisubstituted cyclobutanes with continuous stereocenters. Note that this tandem process features a good regio- and diastereoselectivity profile. Isotopic labeling experiments support the “exo to endo” migration of the double bond to a coordinated cyclobutene that is responsible for the deuterium incorporation observed in the cyclobutane product.