Palladium catalysed cascade cyclisation-anion capture, relay switches and molecular queues

Cyclic carbopalladation can be achieved by a group of related reactions that provide versatile and powerful methodology for the construction of carbocyclic and heterocyclic rings. These ring forming processes are marked by their tolerance of a wide range of functionality together with their ability to process a variety of starter species and to effect cyclisation onto all types of C-C unsaturated bonds. Substantial additional pre- and post-cyclisation functionality can be incorporated via cyclisation-anion capture and/or polycomponent cascades that switch between inter- and intra-molecular processes. The polycomponent cascades can be regarded as proceeding via molecular queuing processes and when gaseous reactants are employed the queuing processes are sensitive to pressure. These wide ranging processes occur with excellent chemo-, regio- and stereo-selectivity and allow incorporation of precisely located complex functionality whilst generating bridged, fused and spirocyclic systems and multiple C-C/C-heteroatom bonds. (C) 1999 Elsevier Science S.A. All rights reserved.