Synthesis and ring transformations of 1-amino-1,2,3,9a-tetrahydroimidazo[ 1,2-a]indol-2(9H)-ones

Heating 1-carbamoylmethyl-2,3,3-trimethyl-3H-indolinium chloride in the presence of hydrazine bishydrate produces regioselectively the five-membered heterocycle 1-amino-1,2,3,9a-tetrahydro-9,9,9a-trimethylimidazo[1,2-a]indol-2(9H)-one. The assignment of the structure is based on extensive H-1, C-13 and N-15 NMR spectroscopic studies. No ring-chain tautomerism of the 1-amino-1,2,3,9atetrahydroimidazo[1,2-a]indol-2(9H)-one was observed to open-chain hydrazides or the corresponding six-membered 1,2,10,10a-tetrahydro[1,2,4]triazino[4,3-a]indol-3(4H)-one. Further transformations of 1-amino-1,2,3,9a-tetrahydroimidazo[1,2-a]indol-2(9H)-one were performed by treatment with aromatic aldehydes, acid chlorides and isocyanates giving access to 40 novel hydrazones, N,N'-diacylhydrazines, N-acyl-N'-carbamoylhydrazines and 1,3,4-oxadiazoles, (c) 2006 Elsevier Ltd. All rights reserved.