Tandem and Concurrent Cycloaddition/Annulation Reactions of Chromium Alkynyl Carbene Complexes

Article abstract of DOI:10.1021/ja00336a041

The Diels-Alder reaction of α,β-acetylenic chromium carbene complexes readily occurs with a number of dienes at ambient temperatures.These alkynyl complexes can serve as synthons for substituted propiolate esters since the chromium pentacarbonyl group of the cycloadducts can be easily oxidatively removed with Me2SO.The cyclohexa-2,5-dienyl chromium carbene complexes which are obtained from the Diels-Alder reactions are found to undergo annulation reactions with acetylenes to give dihydronaphthols or decalatrienones.The cycloaddition and annulation reactions may be carried out in tandem or concurrently with the alkynyl carbene complex, the diene, and the acetylene all in one pot.The alkynyl carbene complex will chemoselectively react with a diene in the presence of an acetylene, and the resultant cycloadduct will chemoselectively react with an acetylene in the presence of a diene to give up to as high as 92 percent yield of dihydronaphthol products.Some specific examples of the tandem and concurrent cycloaddition/annulation sequences are reported which suggest attractive applications to be made in synthetic organic chemistry.