Key points are not available for this paper at this time.
Abstract A formal 3 + 3 cycloaddition strategy for constructing complex heterocycles is reviewed here. This formal cycloaddition involves condensation of α,β‐unsaturated iminium salts with 1,3‐dicarbonyl equivalents. These reactions consist of a Knoevenagel‐type condensation followed by a reversible 6π‐electron electrocyclic ring‐closure. They constitute a stepwise formal 3 + 3 cycloaddition protocol with the net result being the formation of two σ‐bonds in addition to a new stereocenter adjacent to the heteroatom. This review describes in some detail, but not comprehensively, some precedents, problems, solutions, and stereochemical mechanistic issues, and focuses on applications of this formal cycloaddition strategy in natural product synthesis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Hsung et al. (Mon,) studied this question.