Sulfurization reagents

Sulfation and Sulfonation. a-Olefin reactions involving the introduction of sulfur-containing functional groups have commercial importance. As with many derivatives of olefins, several of these products have appHcations in the area of surfactants (qv) and detergents. Typical sulfur reagents utilized in these processes include sulfuric acid, oleum, chlorosulfonic acid, sulfur trioxide, and sodium bisulfite. 

Later, this reaction was applied to thioepoxidation, thereby dithiiranone 57 (or oxathiiranethione) acting as a sulfurization reagent (85JOC3228). 

Mikolajczyk, M. Drabowicz, J. Kielbasihski, P. Chiral Sulfur Reagents, CRC Press, Boca Raton, 1997. 

Scheme 31 Synthesis of ruthenium and rhenium disulfido complexes by the use of (TMS)2S as a sulfur reagent...

M. Mikolajezk, J. Drabowicz and P. Kielbasinski, in Chiral Sulfur Reagents, CRC Press, USA, 1997. 

Reactants with internal nucleophiles are also subject to cyclization by electrophilic sulfur reagents, a reaction known as sulfenylcyclization.92 As for iodolactonization, unsaturated carboxylic acids give products that result from anti addition.93... 

The classification adopted in this review is by type of sulfur reagent it is useful to list by section the more important heterocycles that can be made thiiranes, II,C, IV,B, VIII,D thietanes and thietanones, V,B,2, VI,B,... 

Nitrile sulfides (37) have some, admittedly slight, structural affinity with the other nitrogen-sulfur reagents discussed in Section IV. They are unstable reactive intermediates that can be generated by the thermolysis of 1,3,4-oxathiazol-2-ones (38) or of 1,3,4-oxathiazoles (39).41 42 An alternative preparation is by the elimination of 2 moles of hydrogen fluoride from imini-sulfur difluorides (Scheme 5).43 Nitrile sulfides (37) are capable of undergoing... 

The use of other phosphorus-sulfur reagents for heterocyclic synthesis appears rare. It would be interesting to investigate in more detail the reaction of compounds, such as the phosphine sulfides, with organic substrates. Triphenylphosphine sulfide is an effective sulfur transfer agent, as it converts oxiranes into thiiranes in good yield. The reaction proceeds with retention of configuration.128... 

Few examples have been reported of metals coordinated to six-membered boron-sulfur heterocycles. Ashe et al. prepared 4-methyl-l,4-thiaborin (SC4H4BMe) which forms a stable molybdenum tricarbonyl sandwich complex 144.158 jn g etjert s laboratory, the reaction of the diborolyl complex 33 (Section 3.01.3.2) with COS afforded the dinuclear complex 145 whose structure was determined crystallographically.36 Other products, not involving boron-sulfur heterocycles and hence outside the scope of this discussion, were obtained via the treatment of 33 with different sulfur reagents such as CS2.36... 

In recent years three other examples of asymmetric induction have been described in the literature in which the chiral sulfur reagent that induces optical activity is converted into another chiral sulfur compound. The first reaction of this type is the chlorination of 2,2-diphenylaziridine (265) by means of the optically active A -chloro-phenylmethylsulfoximide (266), affording optically active A -chloro-2, 2-diphenylaziridine (267) and the unsubstituted sulfoximide 149 (197). In this case asymmetric induction is observed on the nitrogen atom. 

In many synthetic applications, the sulfur or selenium substituent is subsequently removed by elimination, as will be discussed in Chapter 6. Arenesulfenyl halides, ArSCl, are the most commonly used of the sulfur reagents. A variety of electrophilic selenium reagents have been employed, and several examples are given in Scheme 4.3. 

These reactions have undergone extensive development and have proven to be general for the synthesis of these ring systems from any substituted o-diamine . The choice of the sulfur reagent, thionyl chloride, sulfur dioxide, sulfinylaniline or sulfur monochloride, depends upon the nature of substituents present. 

We therefore needed a ready synthesis of the 1,6-epithio epoxide 119. Normally, for such syntheses, the sulftir atom is introduced at an early stage [64]. However, it appeared to us that a suitable doubly-activated sugar such as 120 should be capable of direct conversion to the 1,6-epithio sugar 121 by treatment with some type of sulfur reagent. Indeed, the o-glucosyl bromide 122 was easily prepared and, upon treatment with either hydrogen sulfide and triethylamine in DMF or benzyltriethylammonium tetrathiomolybdate in chloroform, gave the... 

Formation of a bond between two heteroatoms is also of considerable utility in the synthesis of sulfur-containing polyheteroatom systems. Reaction of 1,5-dinucleophiles with electrophilic sulfur reagents such as thionyl chloride or sulfur dichloride leads directly to the heterocycles (e.g. equation 55). A fuller discussion of these types of reaction is given in Chapter 2.28. 

P. Metzner and A. Thuillier, Sulfur Reagents in Organic Synthesis, 1994... 

Sulfur reagents are strong nucleophiles, and heteroaryl phenyl ethers have been prepared by treating thiophenol with chloro and bromo heterocycles under PT conditions.196,219... 

Reaction of a Sulfur Reagent and a Four-carbon Chain 881... 

Miscellaneous reactions of four-carbon units with sulfurizing reagents 890... 

FORMATION OF TWO BONDS TO FORM A THIOPHENE RING 3.15.3.1 Reaction of a Sulfur Reagent and a Four-carbon Chain... 

A variety of sulfur reagents have been used for the dehydrohalogenation of vic-dihaloalkanes to alkenes. Aqueous sodium trithiocarbonate in the presence of a phase transfer catalyst was reported to give high yields under very mild conditions [217]. A radical mechanism involving a one-electron transfer was proposed as the first step in this reductive elimination. 

Fluoroaromatic compounds react with nucleophilic sulfur species, resulting in single, multiple, or complete replacement of fluorine, to form C —S bonds. The extent of fluorine substitution depends on (1) the solvent used, (2) the nature of the sulfur reagent, (3) the ratio RS / ArF, (4) the reaction time and temperature, and (5) the nature of the fluoroaromatic compound. 

When l,l,3,3-tetramethyl-2,l,3-thiadisilolane is used as sulfur reagent, another type of reaction takes place. Two molecules of the fluorine-containing compound become linked via a sulfur bridge with elimination of a fluorine atom from each.31 Thus, (4-fluorophenyl)phenyl-methanone reacts with l,l,3,3-tetramethyl-2,l, 3-thiadisilolane in TV. A -dimethylacetamide (with catalytic amounts of CsF, 12 h at 120 C, under N2) to give bis(4-bcnzoylphenyl) sulfide in 81 % yield.31... 

---