Tetrahedron 54 (1998) 223-232 TETRAHEDRON Pergamon One pot synthesis of 1,2J-benmdithiaml-6-ones Cecilia Polo, Vicente Ramos, TomPs Torroba* Departamento de Quimica Organica, Facultad de Veterinaria, Universidad de Extremadura, 10071 Cbceres, Spain Oleg A. Rakitin N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect, 47, 117913 Moscow, Russia Charles W. Rees* Department of Chemistry, Imperial College of Science, Technology and Medicine, London. SW7 2AY, UK Received 6 October 1997; revised 27 October 1997; accepted 30 October 1997 Abstract: The reaction of p-benzoquinone-4-oximes with disulfur dichloride affords the red 6H-1,2,3- benzodithiazol-6-ones. Some ring chlorination occurs, but 2,6-substituents are retained in the products except for a ferr-butyl group, which is, exceptionally, replaced by chlorine. 1,4-Naphthoquinone 4-oxime and 1,2-naphthoquinone 2-oxime similarly give the red 4-chloro-SH-naphtho[ I ,2-d[ 1,2,3]dithiazol-5-one and the blue 9-chloro-4H-naphtho[2,3-d][ 1,2,3]dithiazol-4-one respectively. A unified set of mechanisms is proposed for all of the reactions. 0 1997 Elsevier Science Ltd. All rights reserved. INTRODUCTION The conversion of 2-unsubstituted aromatic amines into 1,2,3-benzodithkolium chlorides by disulfur dichloride (Herz reaction) is employed in the dye industry for the synthesis of various heterocycles such as thioindoxyls and thioindigos, benzothiazoles, phenothiazines, benzothiadiazoles, and thiazolobenzo-2.1,3- thiadiazoles.’ Formation of the benzodithiazolium system is accompanied by chlorination of the carbocyclic ring.’ Electron withdrawing groups are often displaced by chlorine but electron donating groups are unchanged.3 Some heterocyclic amines also react with disulfur dichloride, S2C12, affording 1,2,3-dithiazolium chlorides without further chlorination.4 In this way, fused thiopheno- and pyrazolo-1,2,3-dithiazoles have been prepared. 1,2,3- Benzodithiazolium salts have been the subject of much research because of their pharmaceutical applications,’ but neutral 1,2,3-benzodithiazoles are scarcely known, with the exception of a few benzodithiazole-2-oxides.h Although formed in very low yield, a benzodithiazole fused to a dithiatriazepine ring has been fully described,’ showing that quinonoid 1,2,3-benzodithiazoles may be obtained as stable compounds. We have previously synthesised cyclopenta- and cyclohepta-1,2,3-dithiazoles’ as well as dithioles’ by reaction of cyclic oximes or diisopropylamines with S$&. A related reaction applied to quinone monoximes could provide a rational synthesis of quinonoid benzodithiazoles and in this paper we describe such an easy one-pot method to yield 6H- 1,2,3-benzodithiazol-6-ones, together with the scope and limitations of the method. 0040-4020/98/$19.00 8 1997 Elsevier Science Ltd. All rights reserved. PII: S0040-4020(97)10272-1