Intramolecular Diels-Alder Reactions of Indole-3-acrylates

Article abstract of DOI:10.1021/jo00230a002

Indole-3-carboxaldehyde was alkylated to give the N-alkylated indole-3-carboxaldehydes 1a-d and 4.These ware extended by two carbon atoms with methyl (triphenylphosphoranylidene)acetate to the methyl indole-3-acrylates 2a-d and 5.When these indoles were heated to 300 deg C the (tetrahydro)carbazoles 3a-d and 6a were obtained.Compound 3c represents a novel ring system.Indole-3-carboxaldehyde was also acylated to give the N-acylated indole-3-carboxaldehydes 1e,f.These were carbon extended to the N-acylated indole-3-acrylates 2e,f which upon heating to 300 deg C gave the (tetrahydro)carbazoles 3e,f and 6b.