Orthoester in Cyclodehydration of Carbamate-Protected Amino Alcohols under Acidic Conditions

The first acid-promoted reaction system to form azaheterocycles from N -carbamate-protected amino alcohols is described. The reaction involves the activation of the hydroxyl group via the use of orthoesters. Despite the reduced nucleophilicity of carbamate nitrogen, this reaction system provides several types of pyrrolidines and piperidines in good to high yields. Using this protocol, prolinol derivatives can also be synthesized from carbamate-protected amino diols with regio- and stereoselectivity.