1-Aza-1'-Oxa(3,3)sigmatropic rearrangement: Synthesis of N-alkylindoles and 2,3-Dihydro-1h-Pyrrolo (1,2-A) Indole-9-Carboxylates

201 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1980.The {3,3}sigmatropic rearrangement of N-alkyl-N-aryl-O-acetoacetylhydroxylamines gives N-alkyl indoles in moderate yields under mild conditions. The substituted hydroxylamines were prepared by the condensation of aldehydes and ketones with an arylhydroxylamine and reduction of the nitrone so formed with sodium cyanoborohydride. This procedure affords high yields of N-alkyl-N-arylhydroxylamines and is tolerant of a wide variety of substituents.O-Acetoacetylhydroxylamines formed by reaction with diketene, (beta)-keto esters, and (beta)-keto acids undergo rearrangement and dehydration to the N-alkylindoles.A new synthetic method for the preparation of 2,3-dihydro-1H-pyrrolo{1,2-a}indole-9-carboxylates has been developed. The condensation of substituted N-arylhydroxylamines with ethyl 6-oxo-2-hexynoate in the presence of sodium cyanoborohydride afforded moderate yields of the pyrroloindoles over a five-step sequence of reactions. Sodium cyanoborohydride reduction of the nitrone condensation product, intramolecular conjugate addition of the hydroxylamine oxygen, and 1-aza-1'-oxa{3,3}sigmatropic rearrangement gives rise to a proposed benzazocinone intermediate. Transannular cyclization and dehydration then furnishes the pyrrolo-indolecarboxylates.7-Methoxymitosene has been prepared from ethyl 2,3-dihydro-5-methoxy-6-methyl-1H-pyrrolo{1,2-a}indole-9-carboxylate by a short synthetic route which is adaptable for use in the synthesis of other analogues of the mitomycins.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD