Cyclopentathiadiazines, Cyclohepta- and Cyclopentadithiazoles: New Materials and a Rich Heterocyclic Chemistry of Cyclic Enaminonitriles

3-Amino-1H-indene-2-carbonitrile and 2-amino-3H-indene-1-carbonitrile reacted with SCl2, iBu3N and NCS to give benzocyclopenta[1,2,6]thiadiazines, and whilst 2-aminocyclopent-1-enecarbonitrile gave, under the same conditions, a cyclopenta[1,2,6]thiadiazine, its reaction with mixtures of S2Cl2, SCl2 and iBu3N under different conditions gave, selectively, an isothiazolo[3,4-d]cyclopenta[1,2,3]dithiazole and new cyclopenta[1,2,3]dithiazole derivatives. Similarly, 2-aminocyclohept-1-enecarbonitrile reacted with SCl2, iBu3N and NCS to give a formally antiaromatic cyclohepta[1,2,3]dithiazole. Some of the compounds obtained showed characteristics useful as new materials, for example, as liquid crystals and near-infrared dyes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)