Sigmatropic rearrangements of 'onium' ylids.
Rearrangement reactions occupy a special place within the canon of organic synthesis, by virtue of the inherently high efficiency of chemical processes which form and break bonds by redistribution of electrons around a retained atomic framework. Within the broader class, sigmatropic rearrangements are chemical processes defined by mechanisms involving unimolecular migration of sigma-bonds with concomitant redistribution of one or more pi-bonds. Sigmatropic processes may involve uncharged or charged species, with the charges located on carbon or heteroatoms; the latter reaction type is the subject of this tutorial review.
Department of Chemistry, University of Reading, Reading, UK RG6 6AD. j.b.sweeney@rdg.ac.uk
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Sweeney