Diels–Alder reactions of 2,3-dimethylenepyrrole analogues; a new synthesis of indoles
Abstract
The pyrano[3,4-b]pyrrol-5(1H)-ones (4) are stable cyclic analogues of 2,3-dimethylenepyrrole, and undergo Diels–Alder reaction with a range of acetylenes, or acetylene equivalents, to give, after loss of carbon dioxide, indoles.