1: 1.) n-butyllithium / tetrahydrofuran / 1.) -23 deg C, 1 h, 2.) -20 deg C 2: pyridinium p-toluenesulfonate / CH2Cl2 / Ambient temperature View Scheme

pyridinium p-toluenesulfonate in dichloromethane Ambient temperature; Yield given. Yields of byproduct given. Title compound not separated from byproducts;