1,2-Benzoisothiazole 1,1-dioxides

A superior method was used for the dehydroxylation of estrone in 96% yield by initial reaction with 3-chloro-1,2-benzoisothiazole-1,1-dioxide (RCI) in refluxing toluene containing triethylamine (yield 100%) followed by heating in benzene with aqueous sodium hypophosphite for 15 minutes in the presence of 10% Pd-C (ref.54). 

The Diels-Alder cycloaddition of chiral cyclic 2-amidodienes, derived from chiral a-allyl allenamides, with enones yielded optically enriched [2.2.2]bicyclic adducts with dr up to >95 5. In the presence of HOMO-raised trienamines, e-deficient l-aza-l,3-butadienes containing 1,2-benzoisothiazole-1,1-dioxide or 1,2,3-benzoxathiazine-2,2-dioxide react as dienophiles in normal-electron-demand Diels-Alder reactions rather than the corresponding inverse-electron-demand versions. The Fe(III)-catalysed benzannulation of 2-(2-oxyethyl)-benzaldehydes with alkynes produced naphthalene derivatives in high yields (99%) under mild reaction conditions. ... 

Benzoisothiazole dioxides undergo [2+2] cycloaddition with 1-diethylaminopropyne followed by ring expansion to give 3-diethylamino-l,2-benzothiazepine 1,1-dioxides (378 R1 = Me, R = Et) (76H(5)95). JV-Tosylsulfimines, e.g. (386), are converted into 1,2-benzothiazepines (388) in high yield when treated with triethylamine in benzene under reflux. In the absence of base the intermediate (387) can be isolated (80JCS(Pl)2830, 81JCS(P1)1037). 

Benzothiophenes, (in), prepared by Yamasaki (2) and thiazole-benzoisothiazole dioxide derivatives, (IV), prepared by Petry (3) were effective as cGMP-PDE inhibitors and used as blood sugar level-depressing agents in the treatment of insulin resistance syndrome associated with Type II diabetes. 

Ahn et al. applied the asymmetric transfer hydrogenation of benzoisothiazole dioxides to the formation of chiral sultams [197] that are useful as chiral auxiliaries [198]. 

Few racemic alkyl p-tolyl sulphoxides were prepared in rather low yields (16—40%) by the reaction of Grignard reagents with mixed anhydrides 108,109 and compound 110 formed in situ from p-toluenesulphinic acid and 3-phthalimidoxy-l,2-benzoisothiazole 1, 1-dioxide (equation 59). The mixed anhydrides 109 or 110 when reacted with cyclopen-tene and cyclohexene enamines 111 gave the corresponding a-ketocycloalkyl sulphoxides 112 in low yields (10-41%) along with small amounts of several by-products such as disulphides and thiosulphonates (equation 60). 

Benzoisothiazole-2,2-dioxides undergo autoxidation under basic conditions in the presence of TBA-Br to yield 2-aroylaniline derivatives (Scheme 10.6) and the more simple diarylmethylsulphones produce diaryl ketones (Table 10.29) [1],... 

Fluoro-3,3-dimethyl-2,3-dihydro-l,2-benzoisothiazole 1,1-dioxide ()V-fluoro-2,oc-... 

A-Tosylsulfimines, e.g., 250, are converted into 1,2-benzothiazepines 252 by triethylamine (Scheme 142). In the absence of base the intermediate 251 can be isolated <1981J(P1)1037>. 1,2-Benzothiazepine 1,1-dioxides 254 are prepared by ring expansion of the 1,2-benzoisothiazole derivatives 253 upon treatment with 1-diethylamino-l-propyne (Scheme 143) <1996T3339, CHEC-III(13.07.4.2)241>. 

NaFIMDS = sodium hexamethyidisilazanide NFOBS = 2-fluoro-l,3.2-benzo-dithiazole 1.1,3,3-tetroxide 2 = 2-fluoro-3,3-dimethyl-2.3-dihydro-l,2-benzoisothiazole 1,1-dioxide 3 = l-fluoro-2,4,6-timethylpyridinium trifluoromethanesulfonate. 

For the synthesis of A -Nps amino acid derivatives various Nps-donating reagents have been proposed (Scheme 46) (1) 2-nitrophenylsulfenyl chloride (Nps-Cl, 92),P5i-592,607] 2) 2-nitro-phenylsulfenyl thiocyanate (Nps-SCN, 95), (3) 4-nitrophenyl 2-nitrophenylsulfenate (Nps-ONp, 93), and (4) 2-(2-nitrophenylsulfanyl)-l,2-benzoisothiazole-3(2/i -one 1,1-dioxide (Nps-saccharin, 94). ... 

Phenylvinyl)-l,2-benzoisothiazole A,A-dioxide 40a and its /)-methoxy derivative 40b show loss of SO2 followed by that of a hydrogen atom. In this case, a highly stable aromatic fused system may be formed <2000THS(4)405>. As an example, fragmentations of 40a are shown in Scheme 2. 

For 3-dicarbethoxymethylene-benzoisothiazole A,A-dioxide 41, the most abundant fragment ions are produced by decomposition of the side-chain (Scheme 3) <2000THS(4)405>. 

In one of the indirect approaches to plant health, long advocated by Horsfall (1972), probenazole (5. 7), which has no anti-fungal properties, is used to prevent infection of rice plants. It does this by preventing the mature hardening of piercing organelles on the fungus so that they cannot penetrate even cellulose film. This substance, 3-allyloxy-l,2-benzoisothiazole-1,1-dioxide, and penta-chlorobenzyl alcohol seem to act by the same mechanism (Sekizawa etaL, 1982). 

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