Chemistry of 4-chloro-5-cyano-1,2,3-dithiazolium chloride

The title compound 2, modelled on Appel salt 1, reacts as rapidly as 1 with phenols and anilines; since it lacks a good leaving group at the highly el ectrophilic C-5 position there is not one low energy reaction pathway, as t here is with I, and the reactions are complex giving more products in lower yields. With phenols it gives 2-aminobenzofuran-3-carbonitriles 3 resultin g from initial nucleophilic attack through the phenolic ortho-carbon (Schem e 1). Aniline reacts with 2 largely through nitrogen to give 2-phenyliminop ropanedinitrile 7 and the amidine 8, the bis-anilinomalononitrile 9 and the thioamide 10, all derived from 7 (Scheme 2). 1,4-Diaminobenzene reacts sim ilarly with 2 to give the mono- and bis-dicyanoimines 22 and 23, whilst 1,2 -diaminobenzene gives the cyclised product 2-aminoquinoxaline-3-carbonitril e 20. 1.8-Diaminonaphthalene gives the sulfur abstraction product, thiadiaz ine 24, and the quinomethane imine 25 and products derived from it (Scheme 7), in keeping with the high reactivity of the naphthalene ring towards ele ctrophilic substitution. In all of these reactions with aromatic amines, sa lt 2 is acting as an equivalent of NC-C-CN (umpolung of malononitrile) whil st with phenols it acts as an equivalent of dicyanocarbene, NC-C-CN.