Thiobenzoyl compounds

A number of general methods for the synthesis of meso-ionic 1,2,4-triazol-3-ones are available. Sodium ethoxide-catalyzed cyclization of 1-benzoyl-l,4-diphenylsemicarbazide (201, R = R = R = Ph, X = O) yielded anhydro-3-hydroxy-1,4,5-triphenyl-1,2,4-triazolium hydroxide (200, R = R = R = Ph). A general route to meso-ionic 1,2,4-triazol-3-ones (200) is exemplified by the formation of the 1,4,5-triphenyl derivative (200, R = R = R = Ph) from A-amino-MA -diphenylbenzamidine (202, R = R = R = Ph) and phosgene. In contrast with this ready meso-ionic compound formation, the corresponding reaction of the iV-methylbenzamidine (202, R = Me, R = R = Ph) did not yield the meso-ionic 1,2,4-triazol-3-one (200, R = Me, R = R = Ph). The product was in fact 3,4-diphenyl-2-methyl-l,2,4-triazol-5-onium chloride (203), which on heating gave 3,4-diphenyl-1,2,4-triazol-5-one (204, R = Ph). The formation of the A-methyl derivative (200, R = Me, R = R = Ph, yield 79%) by heating the 7V-thiobenzoyl semicarbazide (201, R = Me, R = R = Ph, X = S) with potassium carbonate in methyl cyanide has been reported. Another synthesis of A-methyl derivatives (200, R = Me) involves methylation of 3-methyl-4-phenyl-l,2,4-triazol-5-one (204,... 

The corresponding compound with thiobenzoyl diazenido ligands also has been prepared (37). 

The reaction between thioacylformamidines and ketenes leads to thiazine-6-ones (29) (Scheme 16) (75T3055). 4-Amino-4//-thiazines (30) are obtained by condensation of thioacylformamidines with acetylenic compounds (Scheme 17) (85JOC1545). Thiobenzoyl-1 and )V,A/-diethylami-nothiocarbonyl isocyanates and isothiocyanates have been reacted with enaminoketones and ynamines. Enaminoketones and ynamines reacted with thiobenzoyl isocyanate give thiazine-4-ones 31 and 32, respectively (Scheme 18) (76BCJ2828 85ZC324). 

The reaction of a thioamide or thiourea and an A/,(V-dimethylacylamide dimethyl acetal at room temperatures produces imino derivatives of type (327). The latter compounds readily condense with amino transfer reagents such as hydroxylamine-O-sulfonic acid and mesitylsulfonyloxyamine (MSH) to afford (301 R=H, Me R = aryl, ArNH, 4-pyridyl) in excellent yields. An unusual reaction of the E category is the condensation of nitrosobenzene with thiobenzoyl isocyanate, which produces the thiadiazolone (328) in 58% yield (Scheme 118) (73CB1496). Presumably, nitrobenzene is another reaction product, although this has not been characterized. 

The interesting and unusual spectroscopic properties of acylsilanes have received considerable attention.6a,b Unfortunately, a similar systematic study for thioacylsilanes has not been done because of their low thermal stability. These compounds are blue materials [ -max(CCl4) = 678 nm for lb, 692 nm for la,13 and 612 nm for lg16], and are generally liquids except thiobenzoyl-triphenylsilane la, 2,4,6-trimethyl-thiobenzoyltrimethylsilane Is, and 3,5-di-terf-butylthiobenzoyltriphenylsilane le which are solids. 

R = Ph) is also formed in the reaction between diazomethane and thiobenzoyl chloride, probably via a 1,3-dipolar addition of diazomethane to the thiocarbonyl group. Similar additions have been observed by Huisgen et The reaction between thioacyl chlorides and diazo compounds was first studied by Staudinger and Siegwart.i 3 (R = Ph) has been prepared by cyclization of 11 with triethylortho-formate, and also from 2-phenyl-1,3,4-oxadiazole and phosphorus pentasulfide. ... 

Contrary to carboxylic acids which, under normal conditions, only give salts with amines, dithiocarboxylic acids, RCS2H, are quite reactive in nucleophilic displacement reactions. However, the compounds are unpleasant to handle and, due to their limited stability, often give only low yields of thioamides in the reaction with amines.The approach was successfully employed in the synthesis of thiobenzoyl azolides, e. g. in the formation of (7) according to equation (4). °... 

The cycloaddition of methyl acrylate with Af -thiobenzoyl-iV,7V-dimethylformamidine (230) under pressure affords the 4-(A, A -dimethylamino)-5,6-dihydro-4/f-l,3-thiazine (231). When this compound is treated with methyl iodide and triethylamine an elimination reaction ensues to give 6H-... 

Thiobenzoyl isocyanate (313) may contribute four of the atoms (S—C—N—C) of the 1,2,4-thiadiazole ring system, the fifth being provided by a suitable nitrogenous compound. The reactant (313) is readily generated in situ from 2-phenylthiazoline-4,5-dione (312) in toluene.235 It reacts with ethereal hydrazoic acid with effervescence to yield 3-hydroxy-5-phenyl-... 

Imino derivatives 100 of compounds of type 95 were also directly prepared from cumulated ylides 82 or 4 and parabanic acid derivatives 99 by a presumed mechanism as depicted in Scheme 22 [70]. Attack of the nucleophilic ylidic carbon atom at the most electrophilic amide-type carbonyl carbon atom, ring opening with loss of phenyl isocyanate, and recyclization by N-C bond formation are the key steps. This reaction is reminiscent of an older one, furnishing 5,5-diethoxy- l-thiobenzoyl-4-triphenylphosphoranylidene-pyrrolidine-2,3-dione 102 from 2-phenylthiazoHne-4,5-dione 101 and 4 [71] in modest yield. 

The action of nucleophilic reagents on the thiadiazolium salts (683) and (685) has been investigated. Hard nucleophiles generally attack a carbon atom, whereas soft nucleophiles react at sulphur. Thus sodium hydroxide reacts with the two salts to yield mainly the benzamidines (684) and (686), respectively, via initial attack at C-5 and subsequent ring opening and loss of sulphur whereas treatment of compound (685) with sodium sulphide, sodium thiosulphate, sodium thio-phenate, or sodium borohydride gives the thiobenzoyl derivative (687) by reaction at the sulphur atom (see Scheme 6). ... 

A series of recent papers documents solid advance within the chemistry of thioacyl isocyanates. Thus a variety of heterocyclic compounds have been obtained in (4+2) cycloaddition reactions of thiobenzoyl isocyanate (276) with aldehydes, diarylketens, ketenimines, benzylideneamines, ... 

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