Aromatic and heteroaromatic annelation studies on 3-[bis(methylthio)methylene]-1-methyloxindole: synthesis of carbazoles and an efficient route to pyrido[2,3-b]indoles

The 3-[bis(methylthio)methylene]-1-methyloxindole (2) is shown to undergo cycloaromatization with allyl and methallyl magnesium chlorides to afford substituted carbazoles. A novel route to 2-substituted-3-cyano-4-methylthio/aminopyrido[2,3-b]indoles has been developed via heteroaromatic annelation of 2 with in situ generated 2-lithioamino-2-substituted acrylonitriles.