Jfp. Andrews et al., PYRROLE-2,3-QUINODIMETHANE ANALOGS IN THE SYNTHESIS OF INDOLES .2. SYNTHESIS AND DIELS-ALDER REACTIONS OF 1,6-DIHYDROPYRANO[4,3-B]PYRROL-6(1H)-ONES, Tetrahedron, 49(33), 1993, pp. 7353-7372
The pyrano[4,3-b]pyrrol-6-ones 7-9, 12 and 13 are stable cyclic analog
ues of pyrrole-2,3-quinodimethane, and undergo Diels-Alder reaction wi
th a range of alkynes to give, after loss of carbon dioxide, indoles.