2.1 -Benzisothiazoles react readily with dialkyl sulphates, alkyl bromides, and alkyl toluene-p-sulphonates at 11 5-1 20" to yield quaternary salts. Such salts are decomposed by aqueous acid or base, affording N-substituted o-aminobenzaldahydes ; the parent o-aminobenzaldehyde can be obtained from the product of the reaction between 2.1 -benzisothiazole and ethyl chloroformate. Bridged binuclear o-aminobenzaldehydes may also be prepared.UNTIL recently, reports of quaternary salts of 2,lbenzisothiazoles were of 3-amino-or 3-azo-substituted derivatives only.24 However, a recent paper 5, gives details of the preparation and ring-opening reactions of simple 2,l-benzisothiazole quaternary salts. The work we now describe, completed before the appearance of this paper: extends the scope of such reactions.2,l-Benzisothiazole itself (I; R1 = H) and its simple derivatives afford quaternary salts (11) in good yield on direct heating with dialkyl sulphates, alkyl bromides, or alkyl toluene-P-sulphonates. The salts (11) are usually obtained as colourless crystalline solids by this procedure; in some cases, however, the salt is obtained asan oil, and is best isolated as the orange crystalline iodide by treatment with aqueous sodium iodide solution.
Alkyl‐ und Aryl‐Sn(IV)‐halogenide bilden mit einem Überschuß an Isochinolin in geeignetem Lösungsmittel die thermisch beständigen 1 22‐ und 1:1‐Komplexe (I) bzw. (II).
Die 2,1‐Benzisothiazole (I) werden mit den Agenzien (II) zu den Salzen (III) quaternisiert, die sich durch kurzes Erhitzen in basischem oder saurem Medium zu den N‐substituierten o‐Amino‐benzaldehyden (IV) zersetzen.
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