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Sythesis of Serotonin Antagonists Using an Intramolecular Diels-Alder Approach
S. Francis*, T. Kiyoi, M. Reid, K. Davies, S. Laats, D. McArthur, H. Feilden, A. M. Easson, Y. Kiyoi, G. Wishart, P. Ray
Merck Research Laboratories, Newhouse, UK
20 July 2011 (online)
Reported is the stereoselective synthesis of tetrahydrobenzopyranopyrrolones (3 and 7) from the cyclobutenes 1 and 4 by an intramolecular hetero-Diels-Alder reaction under microwave irradiation conditions. The careful positioning of an auxiliary carbonyl functionality in the molecule allows the selective formation of the trans-fused ring system 6, or epimerization gives the more stable cis-fused ring system 2. The substrate scope of the process was not widely investigated.