Tiffeneau–Demjanov Rearrangement by Using α-Chloro-α-diazoacetate: A Direct Access to α-Chlorinated Medium-Size-Ring Ketones via Ring Enlargement

Abstract α-Chloro(diazo)acetate can be readily used in an intermolecular ring expansion catalyzed by a boron Lewis acid to construct α-chlorinated medium-size cyclic ketones. This intermolecular Tiffeneau–Demjanov reaction proceeds in good yield from easily prepared or commercially available starting materials and allows the concomitant formation of a tetrasubstituted stereocenter.