Enantioselective Insertion of a Carbenoid Carbon into a C–C Bond To Expand Cyclobutanols to Cyclopentanols

When a carbenoid species generated from a tosylhydrazone is reacted with a cyclobutanol in the presence of a chiral rhodium catalyst, a C–C single bond of the cyclobutanol is cleaved, and the carbenoid carbon is inserted therein to furnish a ring-expanded cyclopentanol in an enantioselective manner