Inter- and intra-molecular reactions of indol-2-yl carbenes and related species. Preparation of 1,1a,2,8b-tetrahydroazirino[2′,3′ : 3,4]pyrrolo[1,2-a]indoles

Abstract

The intramolecular cycloaddition of 2-indolylcarbenes, or their precursors, has been successfully extended to the CN bond of O-methyl oximes. Thus the sodium salts of the tosylhydrazones 10, prepared from the corresponding indole-2-carbaldehydes, decomposed to the azirinopyrroloindoles 11. The N-methoxyaziridine 11a exists as a single invertomer at nitrogen. Several 1-(2-alkynyl)indole-2-carbaldehydes were converted into the corresponding Eschenmoser hydrazones by reaction with trans-1-amino-2,3-diphenylaziridine. No addition of the resulting carbene onto the triple bond occurred upon thermolysis. The only products that were isolated corresponded to attack of the carbene on the solvent. In one case the carbene could be trapped bimolecularly to give an indolyl substituted cyclopropane derivative.