Neighbouring-group effects in heck reactions

The Heck reaction is a widely used carbon-carbon bond forming process in organic synthesis. A prominent variant that has found widespread application in targeted complex-molecule synthesis is the asymmetric intramolecular Heck reaction. This methodology has outshone another powerful facet of Heck chemistry that has been prospering in recent years, namely heteroatom-directed Heck reactions. Initially designed to achieve high regiocontrol in intermolecular reactions, this technique has recently been successfully applied to highly diastereoselective and even enantioselective substrate-directed inter- as well as intramolecular Heck reactions. This microreview delineates, for the first time, the evolution of this chemistry from regio- to diastereo- and, finally, enantioselective transformations. Flexible syntheses of stereodefined, multi-arylated alkenes, the diastereoselective construction of tertiary and quaternary carbon centres, as well as combining substrate- with catalyst-control in an enantioselective transformation are covered. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).