Sulfur-transferring reagent

Dithiatopazine 73 serves as a sulfur-transfer reagent under thermal conditions. Tlius, heating 73 and diene 130 in toluene at 100°C formed a cyclic disulfide 131 (25%) and a tetrasulfide 132 (28%) with the formation of the alkene 118 (90%). Under similar conditions, the highly strained acetylene 133 was converted to the 1,2-dithiete 134 (65%) and the congested thiophene 135 (12%) (90JA3029). 

It has been reported that the zinc hexasulfido complex, Zn(S6)(TMEDA) (TMEDA=] r,] T,N, N -tetramethylethylenediamine) acts as a sulfur transfer reagent in an analogous manner as the above-mentioned titanium polysulfido complexes. The sulfur transfer reaction between Zn(S6)(TMEDA) and TiCp2Cl2 cleanly proceeds at room temperature to afford ZnCl2(TMEDA) and TiCp2S5 together with Ss (Scheme 51) [132]. This result suggests that... 

The bisazolylsulfides shown below are much better sulfur transfer reagents than SXC 2 (x — 1, 2). Moreover they are reactive toward alcohols and primary and secondary amines. 

Thionyl chloride (SOCl2) is the most versatile of all sulfur transfer reagents in heterocyclic synthesis. The sulfur-oxygen bond renders the sulfur atom more electrophilic the possibility of ready removal by elimination of the oxygen atom allows easy aromatization of many of the initially formed sulfur heterocycles. Two general reviews of the chemistry of thionyl chloride are available.53 Both cover the literature up to about 1970. 

The remaining four chapters of the present volume involve topics new to the series. Two of them deal with specific groups of compounds (C. J. Moody on Azodicarbonyl Compounds and T. Sasaki on Heteroada-mantanes ) and two others deal with the Use of Transition Organome-tallic Compounds in Heterocyclic Synthesis (J. L. Davidson and P. N. Preston) and Sulfur Transfer Reagents (M. Davis). 

Benzyltriethylammonium tetrathiomolybdate, [BnNEt3]2MoS4, is a useful sulfur transfer reagent which has now been shown to effect a one-pot, three-step sequence of S-transfer— reduction—Michael addition. The intramolecular version successfully produces 1,4-oxathianes from the bromoenone 108 (Scheme 65). In like manner, the bicyclo[3.3.1]nonane skeleton incorporating a thiopyran ring can be constructed . 

The a,a -dioxothione 109 can be generated from indan-l,2,3-trione using potassium thiotosylate as the sulfur transfer reagent and has been trapped as its [4+2]-cycloadduct 110 (Scheme 66). A 1,3-sulfinate migration from S — O is involved . 

But these disulfides 1 do not substitute for sulfur monochloiide, and so S2CI2 has ranked among the best sulfur transfer reagents in inorganic and organic chemistry since its discovery in the late 1800s (1860LA266). 

The known dibromide 464 was converted in good yield to the dinitrile 465 by reaction with buffered potassium or sodium cyanide. Reaction of 2,5-dimethoxycarbonyl-3,4-dicyanomethylthiophene 465 with thionyl chloride and selenium oxychloride gave thieno[3,4-f]thiophene 466 and selenolo[3,4-f]thiophene 467, respectively (Scheme 57) <2002JOC2453>. In the case of thionyl chloride as the sulfur transfer reagent, an intermediate sulfoxide 468 must be involved, which then suffers a spontaneous base-catalyzed Pummerer reaction to give 466 in high yield. 

D. Bhar and S. Chandrasekaran, A simple synthesis of sugar disulfides using tetrathiomolyb-date as a sulfur-transfer reagent, Carbohydr. Res., 301 (1997) 221-224. 

Recent Advances in the Chemistry of Benzisothiazoles and Other Polycyclic Isothiazoles, 38, 105 Sulfur Transfer Reagents in Heterocyclic Synthesis, 30, 47. 

Thioacetamide has been utilized as a sulfur transfer reagent in the synthesis of azuleno[l,2-c]thiophenes <02H(58)405>. 

A sulfur-transfer reagent was used for the synthesis of 1,2-dithiepines 144, potential radiation-protection drugs, from the ditosyldisulfide 143 . 

---