Heterocyclization of allenes catalyzed by late transition metals: Mechanisms and regioselectivity

Abstract

Regiocontrolled metal-catalyzed preparations of enantiopure tetrahydrofurans, dihydropyrans, and tetrahydrooxepines have been developed starting from γ-allenols derived from 4-oxoazetidine-2-carbaldehydes and D-glyceraldehyde. Regioselectivity control in the O-C functionalization of γ-allenols can be achieved through the choice of catalyst, protecting group, or tether. Because of the increasing power and availability of computers, and the simultaneous development of well-tested and reliable theoretical methods, the use of computational chemistry as an adjunct to experimental research has increased rapidly. Computational studies can be carried out to assist in understanding experimental data, such as the exploration of reaction mechanisms that are not readily studied by experimental means. As a consequence, density functional calculations were performed to predict the regioselectivity of the γ-allenol cycloetherification to the five-, six-, and seven-membered oxacycles on the basis of the tether nature, the presence of a protecting group, and characteristics of the metals, and to gain insight into the mechanism of the oxycyclizations. The interactions between computational and experimental chemistry are often brief. However, it should be desirable to keep this close association for long periods. This chapter must be considered as an interesting symbiotic relationship on the field of organic synthesis using metal (Au, Pd, and Pt) catalysis. © 2011 Springer-Verlag Berlin Heidelberg.