Synthesis and reactions of 2-bis(methylthio)methylene-1-methyl-3-oxoindole: A facile access to benzo- and heterocyclo-fused carbazoles and indoles

The synthesis and reactions of 2-bis(methylthio)methylene-1-methyl-3-oxoind ole 5 as a novel 3-carbon 1,3-bielectrophilic component are described. Thus cycloaromatization of 5 with allyl, methallyl and crotyl Grignard reagents affords substituted carbazoles 12a-c in good yields. Cycloaromatization of 5 with various anions derived from aryl / heteroaryl acetonitriles and ant ipyrine gives novel benzo[c]- (16), naphtho[1,2-c]- (19), indolo[3,2-a]- (2 1), thieno[2,3-c]- (23), pyrrolo[2,3-c]- (25) and pyrazolo[4,3-b]- (29) car bazole ring systems in good yields. Similarly heterocyclo[b]fused indoles l ike pyrido[3,4-b]- (36), pyrido[3,2-b]- (39) indoles and indolo[3,2-b]quino lizinium salt 42 were synthesized by cyclization of 5 with lithioacetonitri le, lithioaminocrotonitrile, and 2-picolyl lithium respectively via our het eroaromatic annelation protocol. (C) 1999 Published by Elsevier Science Ltd . All rights reserved.