Stereoselective synthesis of 2-alkylidene-3-iminoindoles by reaction of 1,1-dianions with oxalic acid bis(imidoyl) chlorides

Treatment of dilithiated nitriles and sulfones with oxalic acid bis(imidoyl ) chlorides resulted in a new cyclization reaction which provided a variety of (3-imino-2,3-dihydro-1H-indol-2-ylidene)-acetonitriles and -sulfones in good yields. The reactions proceeded by condensation of the dianions with the first imidoyl chloride group of the bis(imidoyl) chloride, subsequent i ntramolecular attack of the ortho carbon of the arylimino group onto the se cond imidoyl chloride group, and final aromatization. Excellent stereoselec tivities were observed in most cases.