Intramolecular [3 + 2]cycloadditions: synthesis of 1-methylene-2,3,3a,4,5,9b-hexahydro-1H-benz[e]indenes and an unsuccessful approach to ergot alkaloids

Abstract

1-(1-Hydroxy-2-trimethylsilylmethylprop-2-enyl)-2-(4-substituted-but-3-enyl)-4-methoxybenzenes, prepared by a short synthesis, underwent intramolecular [3 + 2]cycloadditions to produce the title indenes. An analogous intramolecular cycloaddition was attempted with N-benzyl-4-(2-methoxyvinyl)-3-(2-hydroxy-3-trimethylsilylmethylbut-3-enyl)indoline, in an attempt to produce a key intermediate for ergot alkaloid synthesis, but this was unsuccessful.