Comparative study of physical and chemical activation modes. The case of the synthesis of beta-amino derivatives.

The activation of the conjugate addition of amines to alpha,beta-ethylenic substrates is considered. Pressure (physical parameter) is a powerful tool to promote the reaction due to its effect on the nucleophilic attack on the double bond of the acrylic compound with development of zwitterionic species. Combination of pressure and lanthanide catalysis (chemical activation) is a highly efficient multiactivation mode, though it is unable to operate in strongly congested systems. Physicochemical activation by water considerably promotes the synthesis of beta-amino derivatives. However in the case of acrylic esters, it is of little value since the beta-aminoesters formed undergo rapid retro-Michael reactions. Copyright (C) 1996 Elsevier Science Ltd