Synthesis of Sulfides

Sulfides may be prepared by a method analogous to the Williamson ether synthesis. The nucleophile is a thiolate anion rather than an alkoxide. Thiolate ions, RS , are better nucleophiles than alkoxides because sulfur is more polarizable than oxygen. Thus, thiolate ions displace halide ions from alkyl halides by an Sj 2 reaction to give good yields of sulfides. 

Because thiolates are better nucleophiles and weaker bases than alkoxides, elimination reactions do not compete much with substitution reactions. Even secondary alkyl halides can be used to form sulfides. 

Second, because thiols are more acidic (p = 8) than alcohols (p = 16), they are quantitatively converted to thiolates by sodium hydroxide. 

Therefore, it is not necessary to prepare the thiolate in a separate reaction with a sttong base, as is required in the reaction of alcohols with sodium hydride. Sulfides are usually prepared by adding the alkyl halide to a basic alcoholic solution of the thiol. 

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The synthesis of sulfides (172) can be carried out by condensing 2-mercaptothiazoles and the required o-bromo compounds in basic solution at room temperature (488). 

As an illustrative example of this method for electrochemical synthesis of sulfide compounds consisfed in utilizing a sulfur-modified mefal surface as a template for fhe elecfrodeposition of mefal sulfide films, Tacconi and Rajeshwar described fhe firsf aflempl fo obfain all-elecfrodeposifed indium sulfide tiiin films, by a dual batii procedure [95] (cf conventional deposition of indium chalcogenides). The... 

Scheme 28 Synthesis of sulfide tripod-terminated polysilanes.

If the alkylation of thiolate anions is the most common method for the synthesis of sulfides [18], some recent routes make use of a reductive thiolation of carbonyl compounds, as in the following one-pot procedure reported by Olah [19]. The scope of the reaction appears to be very large in the choice of the carbonyl compound as well as that of the thiol partner (Table 2.1). 

A similar approach was used for the synthesis of sulfides 91 by the one-pot reaction from 2,2 -dimethylbinaphthyl 84. After lithiation of 84 with BunLi, the generated dilithio salt was cyclized with CITPh or C P-Bu1 and treated with sulfur to give 91 in 72% and 61% yields <2005TA3416, 2003AGE3509>. 

SYNTHESIS OF DERIVATIVES OF (Me2S)B12H -(l) and (Me B o (2) 3.1 Synthesis of Sulfide Anions by Reactions with Nucleophiles... 

Herriot, A. Picker, D., The Phase-Transfer Synthesis of Sulfides and Dithioacetals. Synthesis... 

Begtnip has also made important contributions to the synthesis of sulfides. For example, in a reaction reminiscent of the ether studies exemplified in Equation 12, a rather regiospecific rearrangement has been observed (Eq. 19). In a later and more detailed study he has investigated the range and limitations of applicability of internal salts such as 8.1-13 (Eqs. 20,21). In this same study it was observed that the isomer of 8.1-13 gives a mixture of products but also some limited synthetic utility (Eq. 22). ... 

Out of these species, the reaction of solvated electrons (650, ) with carbon disulfide is of interest for the synthesis of sulfide nanoparticles. The dissociative electron attachment on SCS (carbon disulfide) is very probable ... 

Fig. 1. Effect of OAS, DCMU and light on sulfite-dependent synthesis of sulfide by pea chloroplasts (85% intact) as determined with a sulfide ion electrode. NaaSOa (1 mM) was added to incubation mixtures A to C but not to D. Values beside the curves represent the rate of sulfide production or consumption in /nmol mg/Chl h . Sulfide consumption in C following the addition of OAS was accompanied by the synthesis of cysteine at a similar rate (from Ng and Anderson, 1979).

The regulation of the biosynthetic pathway for cysteine appears to present the plant with a variety of problems, (a) The formation of cysteine represents the confluence of two separate pathways which produce OAS and the sulfide precursor. Are the rates of these pathways coordinated Is cysteine formation ordinarily limited by the availability of sulfide, OAS, neither, or both (b) In plants, synthesis of sulfide occurs via a pathway which branches after APS to lead to sulfide or to PAPS, the precursor of sulfate esters and, probably, of sulfonolipids. If sulfide formation is regulated, how is provision... 

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