REACTION BETWEEN 2,2′-DITHIODIANILINE AND ETHYL 2-OXO-1-CYCLOALKANECARBOXYLATES

Abstract
A study has been carried out on the acid-catalysed reaction between 2,2′-dithiodianiline (1) and ethyl 2-oxo-1-cycloalkanecarboxylates (2a–d). While the 1,4-benzothiazines 3a, b and benzothiazoles 6a, b are obtained from the keto esters 2a, b, mixtures of the 1,4-benzothiazines 3c, d and 4c, d and benzothiazolines 5c, d are obtained from the keto esters 2c, d. The formation of the benzothiazines 4 falls within the general pattern previously proposed for reactions between 2,2′-dithiodi(aryl- or alkylamines) and ketones. The benzothiazines 3 arise from an acid-catalysed rearrangement of the benzothiazines 4, involving a [1, 3] sulfur migration.