Diels-Alder Adducts of 1-Benzenesulfonylindole-2-acrylates and 1-(Alkoxycarbonyl)-1,2-dihydropyridines. Intermediates for Synthesis of Iboga Alkaloid Analogues

Article abstract of DOI:10.1021/jo00337a003

Diels-Alder reactions between methyl 1-benzenesulfonylindole-2-acrylate and several 1-(alkoxycarbonyl)-1,2-dihydropyridines give protected methyl 7-(2-indolyl)-2-azabicyclo<2.2.2>octene-7-carboxylates which serve as intermediates for the synthesis of analogues of the iboga alkaloids.Methods for deprotection of both the carbamate nitrogen and indole nitrogen are reported.The 7-(2-indolyl)-2-azabicyclo<2.2.2>octene-7-carboxylates show a tendency to undergo fragmentation of the C-1,C-7 bond of the 2-azabicyclo<2.2.2>octene ring, probably by retro-Mannich reactions.Several 6-nor-20-deethyl analogues of catharanthine have been prepared from intermediates derived from the deprotected Diels-Alder adducts.