Structural studies on α-pyrone cycloadducts. Manifestation of the early stages of CO2 extrusion by retro hetero-DielsAlder reaction

Abstract

Structures of the -pyrone (pyran-2-one) cycloadducts 48 show deviations of some bond distances from their normal values, consistent with manifestation of the early stages of the retro hetero-DielsAlder decarboxylation reaction in the ground state structures. Thus the bridgehead CO(CO) and CCO(O) bonds are lengthened and the bridging CO bond is shortened. The degree of lengthening of the CO(CO) and CCO(O) bonds is similar, whereas in the calculated transition state structure there is significant asymmetry in the extent of CCO(O) and CO(CO) bond breaking. © CSIRO 2009.