1.2- Benzisothiazoles 7-acyl

Friedel-Crafts acylation usually fails (72AHC(14)43), but 3-substituted l-methyl-2,1-benzisothiazole 2,2-dioxides can be acetylated at the 5-position (73JHC249). l-Methyl-2,1-benzisothiazol-3-one can be chlorsulfonated at the 5-position (78JHC529). Vilsmeier-Haack formylation causes cleavage of the isothiazole ring (80JCR(S)197). 

Benzisothiazole, 3-hydroxy-acylation, 6, 159 alkylation, 6, 159 chlorination, 6, 160 organophosphorus compounds, 6, 159... 

Displacement reactions of 3-chloro-l,2-benzisothiazole (26) have already been mentioned in Section II,A, 8.18,19 22 24 In some cases this displacement is accompanied by a rearrangement. Boshagen has shown that treatment of the above-mentioned compound (26) with thioacetic acid yields an A-acyl-3H-l,2-benzodithiole (39).31 This rearrangement is analogous to that described in Section II, C, 2 above. 

In view of their importance in enantioselective reactions, many bornane sultams have been synthesized and characterized by MS. Their El mass spectra show molecular ions with low abundance or are absent. N-Substituted bornane sultams generally show the typical fragmentations of the substituents <2000THS(4)405>. 1-Alkyl-7-nitro-2,1-benzisothiazole 2,2-dioxides show elimination of an acyl radical from their molecular ions <1997EJS55>. 

The nitration of 3,5-dimethyl-1,2-benzisothiazole to the 4-nitro and 7-nitro products has been described <91JHC347>. Friedel rafts acylation of 3-methyl-6-methylthio-1,2-benzisothiazole gives the 7-acetyl derivative whereas the 5-methylthio analog fails to acylate <91JHC445>. 

The most general routes to 1,2-benzisothiazoles start from suitable 2-acyl or 2-carboxylic acid derivatives of benzenethiols. A minor improvement in the synthesis of 1,2-benzothiazoles from oximes of 2-acyl benzenethiols is the use of acetic anhydride in pyridine <88CJC1405> (see Section... 

Various routes are used for the synthesis of 1,2-benzisothiazole 1,1-dioxides, and recent advances are the cyclization of 7V-acyl-benzenesulfonamides using two equivalents of LDA, and a one-pot procedure in which or/Ao-lithiated V,V-diphenylbenzenesulfonamides are reacted with nitriles <92J0C5328, 89S394) (see Sections 3.05.9.1.3 and 3.05.9.2.2). 

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