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

Cyclic carbopalladation can be achieved by a group of related reactions tha t provide versatile and powerful methodology for the construction of carboc yclic and heterocyclic rings. These ring forming processes are marked by th eir 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-cyclis ation functionality can be incorporated via cyclisation-anion capture and/o r polycomponent cascades that switch between inter- and intra-molecular pro cesses. The polycomponent cascades can be regarded as proceeding via molecu lar queuing processes and when gaseous reactants are employed the queuing p rocesses 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 a nd spirocyclic systems and multiple C-C/C-heteroatom bonds. (C) 1999 Elsevi er Science S.A. All rights reserved.