Sulfur-or selenium-containing

Bansal et al. found that the recently synthesized phosphatriazolo[l,5- ]pyridines can undergo addition reaction on the phosphorus atom when treated with sulfur or selenium in the presence of a secondary amine <1995ZNB558> (Scheme 15). Thus, reaction of 4 with these reagents yields under mild conditions the sulfur- or selenium containing addition products 51a and 51b in fair yield. 

Fig. 3 List of sulfur- or selenium-containing ligands in Pd-catalyzed reactions of 1,3-diphenylpropenyl acetates with dimethyl malonate (BSA/CH2(C02Me)2)...

It is possible to oxidize an alcohol in the presence of sulfur- or selenium-containing groups (equation 16) using r-butyl hydroperoxide and a diselenide as the oxidizing system (this also oxidizes secondary alcohols, see later).Selenium chemistry can also be used to oxidize benzylic and related primary alcohols to the aldehydes without oxidizing pyridyl (18 equation 17) or thiophenyl (19 equation 18) groups. ... 

IV. Monosaccharides Having a Sulfur- or Selenium-containing Hemiacetal Ring... 

Ferrocene organomercurials were also used to prepare a number of other derivatives, namely, halogen-, sulfur-, or selenium-containing compounds, biferrocenyl, or triphenylmethylferrocene [Nesmeyanov, Perevalova, 0. A. Nesmeyanova 258,259)]. Lithiation or sodium metalation provided even more versatile reagents, the reactions being used by other investigators as well. 

Elemental selenium is an excellent catalyst for fhe carbonylation of a variety of nucleophiles such as amines, alcohols, water, and carbon nucleophiles in the presence of oxygen under mild conditions [114]. In fhe synfhesis of ureas from primary amines and CO, for example (Scheme 15.42), the turnover number reaches ca. 10", giving ureas in almost quantitative yields. Successful applications of this Se/CO system include not only synfhetic reactions with a variety of carbamates, carbonates, and sulfur- or selenium-containing compounds but also metallurgical refining of selenium and several important processes as exemplified by isocyanate synfhesis, fhe water-gas shift reaction, and separation of carbon monoxide [115]. 

Utilization of the conjugate bases of 3-alkyl-l,2-dithiolylium and 3-alkyl-1,2-diselenolylium salts as precursors for sulfur or selenium containing 6,6a2 -triheterapentalenes is a widely used synthetic method. In a slight variation bis-(12, 2-diselenol-l-ylium) salts have been used as precursors. 3-Alkyl-substituted diselenolylium tetrachloroferrates (78) give 6,6aA -diselena-l,2-diazapentalenes (79) upon treatment with benzenediazonium tetrafluoroborate (Equation (23)). The mechanism involves the deprotonation of the 3-methyl substituent followed by rapid electrophilic substitution <93HAC337>. 

Diphenylmethyl radicals with sulfur and sulfur or selenium containing substituents at C (7) ... 

An innovative procedure for the synthesis of sulfur- or selenium-containing lactones from propargyl or homopropargyl alcohols involves the formal addition of ArS-Pd-X or ArSe-Pd-X to a multiple bond as the key stepJ" When a propargyl alcohol is treated with CO under Pd(0) catalysis in the presence of diarylsulfldes or diarylselenides, buteno-lides substituted in the /S-position with S- or Se-based residue are formed (Scheme 30). 

Bacterial MTs have been shown to be capable of adding formaldehyde to cytosine residues in DNA to yield 5-hydroxymethylcytosine (hmC) (Scheme 18.8a) [52]. The enzymes are able to bind hmC-containing DNA and also replace the OH group by sulfur- or selenium-containing moieties (Scheme 18.8b) [53]. 

Medicine and Nutrition. A stabilized buffered suspension of selenium sulfide has been marketed for many years as Selsun Blue (Abbott Laboratories) for control of seborrheic dermatitis of the scalp. A similar sulfur or selenium sulfide shampoo containing a metallic cation complex has been prepared (122). Topical appHcation of selenium sulfide controls dermatitis, pmritis, and mange iu dogs (see Cosmetics Veterinarydrugs). 

Important results and a detailed insight into aqueous chemical deposition processes have been reported and discussed elsewhere for CdSe [248, 249] and ZnS [250, 251] target products. We should note also the work of Davies et al. [252] who described an alternative method for the chemical growth of metal sulfides and selenides on the basis of polysulfide or polyselenide solutions (containing hexa- and tetra-chalcogen anions) formed by the dissolution of sulfur or selenium in hydrazine monohydrate. ... 

The first examples of mononuclear disulfur and diselenium complexes of platinum have been described.330 Reduction of the sterically hindered complex trans- PtC 2( P M e2A r)2] (Ar = 2,4, 6-tris[bis(trimethylsilyl)methyl]phenyl, 2,6-bis[bis(trimethylsilyl)-methyl]-4-[tris(trimethylsilyl) methyl]-phenyl) with lithium naphthalide in THF solution affords the platinum(0) species [Pt(PMe2Ar)2]. Oxidative addition of elemental sulfur or selenium yields the dichalcogenatoplatinum(II) complexes of the type [PtE2(PMe2Ar)2] (E = S, Se) containing a unique PtE2 ring system. The complexes are stable to air in the solid state, but slowly decompose in solution after several days at room temperature. 

The detection of metal-binding proteins, especially of Cd- and Hg-binding metallothioneins or of the merR protein, induced numerous studies of model compounds of Cd and Hg with more or less simple sulfur- and selenium-containing ligands. 

The tricyclic fused heterocyclic system 236 containing a phosphorus atom was constructed by the Diels-Alder reaction. Thus, diazaphospholopyridine 235 was treated with 2,3-dimethylbutadiene in the presence of sulfur or selenium to give the product 236 (Equation 27) <2002JOC9162, 2002T1573, 2005T10521>. 

This review chapter focuses on the syntheses and reactions of these 5-membered heterocyclic ring systems containing nitrogen and sulfur (or selenium) (reported during 2006). The importance of these 71-rich heterocycles in medicinal chemistry and natural products is also covered. 

In the above-described displacement reactions (Sh2) of sulfur- and selenium-containing compounds, the mechanism could either be a synchronous or a stepwise process (Scheme 4.2). Thus, in the Sh2 stepwise mechanism an intermediate sulfuranyl or selenyl radical is formed, followed by a-cleavage [56]. Based on competitive studies, a stepwise process was suggested to occur in the reaction of (TMS)3Si radical with -decylphenylselenide [43]. On the other hand, ab initio calculations supported the synchronous process and the same observations were explained in terms of an overall reversible reaction [57]. 

Many of the molecules are chiral. Six of the above-mentioned compounds contain SeSe bonds and no isolated sulfur or selenium atoms (structural units of type —S—Se—S— or —Se—S—Se—), nine contain SeSe bonds and isolated sulfur or selenium atoms, and 13 contain no SeSe bonds. The number of SeS bonds in these molecules can be either 2, 4, 6, or 8. 

The first structural characterization of a tellurium diimide RNTe(p-N Bu)2TeNR (R = PPh2NSiMe3) was reported in 1994. Subsequently, the synthesis of the symmetric derivative, R = Bu, was achieved by the reaction of Li[HN Bu] with TeClq in a 4 1 molar ratio in toluene. Several LiCl-containing byproducts are also obtained in this solvent. In THF, however, the tellurium diimide, BuN-Te(p-N Bu)2TeN Bu, is obtained in 90% yield and is readily purified." Unlike sulfur or selenium diimides, the tellurium diimides are dimeric and form either cis or... 

Cyclic compounds containing Si2E2 rings (10.56, E = S, Se) are also formed from the reaction of a stable silylene with sulfur or selenium [eqn (10.37)]. The reaction of the divalent germanium compound Ge[N(SiMe3)2]2 with... 

Sulfur or selenium homocycles containing one (or more) exocyclic halogen substituent are prepared by the oxidation of the element with arsenic or... 

Complexes of group VIB elements with sulfur or selenium donor atoms are mainly concerned with complexes of selenium(II), tellurium(II) and tellurium(IV). The structural chemistry of complexes of selenium and tellurium with sulfur- and selenium-containing ligands has been well reviewed in the recent past.11... 

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