Regioselective ad [C,C] connective routes to oxetanes and tetrahydrofuranes

α-Selenoalkyllithiums already used for the regioselective synthesis of epoxides are found valuable building blocks for the synthesis of higher homologues namely oxetanes and tetrahydrofuranes. The general synthetic strategy used is schematized below and represent a formal homologization reaction of epoxides and oxetanes by carbene insertion.