SHORTPAPER	Synthesis 2007: 819-823   DOI: 10.1055/s-2007-965929
© Georg Thieme Verlag Stuttgart · New York
Synthesis of 2-Arylbenzothiazoles by DDQ-Promoted Cyclization of Thioformanilides; A Solution-Phase Strategy for Library Synthesis
D. Subhas Bose*, Mohd. Idrees, Bingi Srikanth
Organic Chemistry Division III, Fine Chemicals Laboratory, Indian Institute of Chemical Technology, Hyderabad, 500 007, India Fax: +91(40)27160387; e-Mail: dsb@iict.res.in; e-Mail: bose_iict@yahoo.co.in;
Received 10 December 2006

Abstract

Several substituted benzothiazoles were synthesized by the intramolecular cyclization of thioformanilides using 2,6-dichloro-3,5-dicyano-1,4-benzoquinone (DDQ) in dichloromethane at ambient temperature in high yields. The resulting 2-arylbenzothi­azoles were separated from the reduced DDQ byproduct 4,5-dichloro-3,6-dihydroxyphthalonitrile by treatment of the reaction mixture with a strongly basic ion-exchange resin. This protocol offers a high degree of flexibility with regard to the functional groups that can be placed on the benzothiazole ring or 2-aryl moiety, which in turn generates scaffolds for parallel synthesis.

Key words

thioformanilide - solution phase - cyclization - 2,6-dichloro-3,5-dicyano-1,4-benzoquinone - benzothiazole - sulfanyl radical