Nucleophilic attack on 2,1-benzisothiazolium salts

Abstract

2,1-Benzisothiazolium salts react with several stabilized carbanions to give products that are derived by attack at the carbon atom of the heterocyclic ring.

The reaction of 2,1-benzisothiazoline-3-thiones with acetylenic reagents

“…Continued reflux gave a dark red solution which on work-up gave a dark red crystalline product, identical to the hypemalent sulfur system 7 a prepared earlier by another method (8). This reaction is therefore related to the formation of 1 ,6,6ah4-trithiapentalenes from 1,2-dithiole-3-thiones by reaction with acetylenes (9-1 1) No products of type 2 or 4 were observed hence if any monoadduct of type 2 is formed it must be rearranging entirely to the system 7, possibly by a reaction catalysed by sulfur 7 similar to that proposed or perhaps the compound 7 is formed from the reaction of the thione with an a-thiocarbene (12).…”

“…The nmr spectrum of 7b 6, 5.16 (2H, s, the benzylic protons), 7.02-8.24 (14H, bands, the aromatic protons), 8 Reaction of N-methyl-1,2-benzisothiazoline-3-thione with dinzethyl acetylenedicarboxylate to form 4 d The thione (0.181 g, 1.0 mmol) and dimethyl acetylenedicarboxylate (0.142 g, 1.0 mmol) in benzene (10 mL) were refluxed 24 h. Evaporation gave a yellow oil which on examination by tlc gave two main yellow bands. The first contained starting thione and the second on elution gave a yellow oil which crystallized under ethanol.…”

The conversions of isothiazolium salts into thiophenecarboxylic ester derivatives

“…For the compound l h , the thiophene derivative 3 c was obtained along with methyl 3-methylamino-2-phenyldithiopropenoate (4). Had attack of the nucleophile occurred at carbon-5 of the salt, methanethiol would likely have been eliminated to provide a reductant, as is known for some 2,l-benzisothiazolium cation reactions (3 have not been able to isolate any reaction product arising from nucleophilic attack at carbon.…”