Lead dithiolates, cyclic

Cyclic disulfides. Reaction of a dithiol (I) with an aqueous solution oflead acetate gives a lead dithiolate (2) in nearly quantitative yield. These react with sulfur in benzene solution at room temperature to give the cyclic disulfide (3) in high yield. 

The treatment of 1,8-dihydroxynaphthalene 426 (X = X = O) with bromochloromethane and K2C03 in DMF gives rise to naphtho[de]-l,3-dioxine 427 (X = X = O, R = R = H) in good yield [83ZN(B)1000]. Acylation of 1,8-naphthalene dithiol 426 (X = X = S) with carboxylic acid chlorides in pyridine leads to mono-S-acyl-derivatives 427 (X = X = S, R = OH) existing in a cyclic form. In sulfuric acid, the latter compounds are converted into naphtho[de]-1,3-dithiinium cations (77BCJ2193). 

Finally, the reaction of 374 with cyclic unsaturated substrates such as 1,3-cyclohexadiene, 1,4-dihydronaphthalene 1,4-dioxide, or acenaphthalene resulted in formation of cycloadducts 405, 407, and 409, respectively. These compounds could be subsequently aromatized by the use of DDQ in the case of 405 and 409 or polyphosphoric acid (PPA) in the case of 407 to generate l,3-dithiole-2-thiones 406, 408, and 410 (Scheme 55) <1996TL8085, 1999TL801>. The compound 410 was further treated with potassium /< r7-butoxide to give the dithiolate intermediate 411, which underwent dialkylation leading to 412 (Scheme 56) <1999J(P2)755, 1999TL801>. 

The interaction of trialkyl or triaryl esters of phosphorotetrathioic acid with P S q at 180° leads to a scrambling of P-SP and P-SC bonds. The products consist of mixtures of 1,3,2,4-dithiadiphosphetane 2,4-disulphides (76) and the perthiodiphosphates (77), the former being formed in large excess. The same products are obtained in essentially the same ratios from P S q and the thiols RSH. In the case of alkane-a,u-dithiols, the products are the dithiaphosphorinanes (78) and (79), both of which are isolable. This last reaction, during which the cyclic acids (80) appear not to be involved, proceeds well for n=2 or 3, but poorly when n=4. ... 

Cyclic Disulphides and Cyclic Diselenides.—Formation. No fundamentally new methods of synthesis of this class of compounds have been reported in the past two years. For l,2>dithiolan the oxidation of l,3>dithiols remains a favoured method, the use of iodine in the presence of triethylamine leading smoothly to 1,2-dithiolans without attendant polymerization. cis- and tra/ -l,2-Dithiolan-3,5-dicarboxylic acids were prepared from a diastereo-isomeric mixture of dimethyl 2,4-dibromoglutarates by sequential treatment with potassium thioacetate and potassium hydroxide in the presence of iodine,and jyn-2,3-dithiabicyclo[3,2,l]octan-8-ol was formed from 2,6-dibromocyclohexanone by successive treatment with potassium thiocyanate, lithium aluminium hydride, and iodine. The stereoselective formation of the less thermodynamically stable alcohol in this case was attributed partly to the formation of chelates with sulphur-aluminium bonds. 2,2-Dimethyl-l,3-dibromopropane was converted into 4,4-dimethyl-l,2-diselenolan on treatment with potassium selenocyanate at 175 °C, but at 140 °C the product was 3,3-dimethylselenetan. Reductive debenzylation of 2-alkylamino-l,3-bis(benzylthio)propanes with lithium in liquid ammonia and oxidation of the resultant dithiols with air afforded 4-dialkylamino-l,2-dithiolans, whilst treatment of a-bromomethyl-chalcone with sodium hydrosulphide gave, as minor product, trans-3 phenyl-4-benzoyl-l,2-dithiolan. Among the many products of thermal decomposition of /ra/ -2,4-diphenylthietan was l,4,5,7-tetraphenyl-2,3-dithiabicyclo [2,2,2]octane. ... 

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