Isothiazoles cyclic

The reaction of 2,5-dimethylisoxazoline-3-thione with 48% HBr produced, among other products, an isothiazole-3-thione, diisoxazole disulfide and 2,5-dimethylisoxazolin-3-one. In contrast, the reaction of 2-methyl-5-phenylisoxazoline-3-thione produced primarily disulfide 80CPB487). The reaction with H2S in 48% HBr produced an isothiazole-3-thione and a cyclic thiazole (Scheme 75) (80CPB487). 

Amines normally have no effect on the isothiazole ring, but 3-chloro-4-nitroisothiazole (49) reacts with cyclic amines such as morpholine at 0 °C to give the enamine (50) (75JOC955). The mechanism may involve attack either at sulfur or at the 5-position (Scheme 6). 

Abstract Synthesis methods of various C- and /V-nitroderivativcs of five-membered azoles - pyrazoles, imidazoles, 1,2,3-triazoles, 1,2,4-triazoles, oxazoles, oxadiazoles, isoxazoles, thiazoles, thiadiazoles, isothiazoles, selenazoles and tetrazoles - are summarized and critically discussed. The special attention focuses on the nitration reaction of azoles with nitric acid or sulfuric-nitric acid mixture, one of the main synthetic routes to nitroazoles. The nitration reactions with such nitrating agents as acetylnitrate, nitric acid/trifluoroacetic anhydride, nitrogen dioxide, nitrogen tetrox-ide, nitronium tetrafluoroborate, V-nitropicolinium tetrafluoroborate are reported. General information on the theory of electrophilic nitration of aromatic compounds is included in the chapter covering synthetic methods. The kinetics and mechanisms of nitration of five-membered azoles are considered. The nitroazole preparation from different cyclic systems or from aminoazoles or based on heterocyclization is the subject of wide speculation. The particular section is devoted to the chemistry of extraordinary class of nitroazoles - polynitroazoles. Vicarious nucleophilic substitution (VNS) reaction in nitroazoles is reviewed in detail. 

Chlorobenz[d]isothiazole-l, 1-dioxide ( pseudosaccharin chloride ) (6)3,24.25, lee, 25i, 26i, 262 displays the reactivity of a cyclic imidoyl chloride263 resembling very much carboxylic acid halides. In previous sections preparation of 3, 4, 5, 13, 68, 86, 89 from 6 has been mentioned. Derivatives of 6 substituted in the phenyl ring have been described.250 Interestingly, Meadow observed231 that crude 6 and material that contained phosphorus pentachloride reacted with thiols more readily than the pure compound. In the reaction of 6 with aromatic sulfonamides, aluminum chloride had been added for activation.252... 

Thiadiazoles are of theoretical interest because as a class they are in a formal sense iso-7r-electronic with thiophene, thiazoles, and five-membered cyclic mono- and diazines. At the same time they are related by physical and chemical similarity to those six-membered cyclic diazines which contain an ethylenic grouping in place of the sulfur atom. 1,2,5-Thiadiazole is thus related to thiophene, isothiazole, imidazole, and pyrazine. It is therefore not surprising that the thiadiazoles have been assigned to the broad class of aromatic structures. 

Besides processes (1) and (2), the reader should be aware that nucleophilic attacks on alkynes are treated in other chapters of this book, dealing with rearrangements, cyclizations, polyacetylenes, cyclic acetylenes and perhaps others. A number of publications overlap with ours in different ways and at different levels -. They treat individual alkynes or families " , e.g. acetylene, diacetylenes , acetylene dicarboxylic esters haloacetylenes , alkynyl ethers and thioethers > ynamines , fluoro-alkynes ethynyl ketpnes , nitroalkynes , etc. synthetic targets, e.g. pyrazoles , if-l,2,3-triazoles , isothiazoles , indolizines S etc. reagents, e.g. nitrones , lithium aluminium hydride , heterocyclic A -oxides - , azomethine ylids - , tertiary phosphorus compounds , miscellaneous dipolar nucleophiles - , etc. The reader will appreciate that all of these constitute alternate entries into our subject. 

The general structures of cyclic sulfoximines are reported in CHEC-II(1996) <1996CHEC-II(3)319> (see p. 348). Very few examples of sulfoximines were reported in the decade under review. The preparation of cyclic sulfilimides 165 and 173 from (R)-l-/>-tolyl-lA-isothiazol-3-ones 164 and diazoalkanes and cyclic dienes, respectively, have been reported (see Section 4.05.5.11). Furthermore, studies on the alkylation of a-sulfonimidoyl carbanions and on their use as chiral ligands in copper reagents were reported (see compounds 227 and 228, Section 4.05.6.3.4). 

Topics reviewed during the year include the photochemistry of indoles, sulfoxides, pyrazoles and isothiazoles, (S-hetero)cyclic unsaturated carbonyl compounds, photoinduced single electron transfer (SET) reactions of amines and of azo compounds, SET reactions of organosilanes and organostannanes with Qo and ketones, photochromic polypeptides and di(hetero)arylethenes, processes in chromophore sequences on a-helical polypeptides,aryl-aryl coupling in furans, thiophenes and pyrroles," [3+2]cycloaddition of aromatic nitriles (and esters) with alkenes, and reactions of benzylsilane derivatives. ... 

These are cyclic organic microbicides containing N and S atoms in the ring system, e.g. thiazole or isothiazole derivatives. 

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