Halides, alkyl reaction with hydrogen sulfide

The reaction of hydrogen sulfide with two equivalents of ethylmagnesium bromide in ether gives a reagent as a viscous mass , which is soluble in THF and reacts with alkyl halides in that solvent to give thioethers [16] ... 

Reaction of an alkyl halide with hydrogen sulfide (9.2). 

Hydrogen sulfide also reacts by nucleophilic substitution with alkyl halides and alcohols under appropriate conditions to form thiols (Scheme 10) (see Chapter 4, p. 42). The reaction with an alkyl halide is generally facilitated by using sodium hydrogen sulfide (NaSH) rather than hydrogen sulfide since NaSH is a much better nucleophile. Hydrogen sulfide also adds to ketones to give gem-dithiols (13) (Scheme 11). 

Sodium hydrogen sulfide can be used for the preparation of thiols (19) by reaction with alkyl halides. A large excess of sodium hydrogen sulfide must be employed to avoid formation of the dialkyl sulfide (Scheme 17) (see Chapter 4, p. 41). 

Several thiols occur naturally for example, skunk secretion contains 3-methyll-butanethiol and cut onions evolve 1-propanethiol, and the thiol group of the natural amino acid cysteine plays a vital role in the biochemistry of proteins and enzymes (see Introduction, p. 2). Primary and secondary thiols may be prepared from alkyl halides (RX) by reaction with excess sodium thiolate (SN2 nucleophilic substitution by HST) or via the Grignard reagent and reaction with sulfur. Tertiary thiols can be obtained in good yields by addition of hydrogen sulfide to a suitable alkene. Thiols can also be prepared by reduction of sulfonyl chlorides (Scheme l).la,2a... 

Carbon disulfide is a valuable synthon (see Chapter 9, p. 147) which can be used for the synthesis of thiocarbonic acid derivatives. Thus, carbon disulfide reacts with ammonium polysulfide or hydrogen sulfide to give trithiocarbonic acid (70) or symmetrical esters (73) after reaction with an alkyl halide. With alkoxides or thiolates, carbon disulfide forms xanthates (77) or S-alkyl trithiocarbonates the latter by further treatment with alkyl, acyl or diazonium halides affords the derivatives (74)-(76) (Scheme 39). 

Reaction of alkyl and aryl halides with salts and derivatives of hydrogen sulfide... 

Rh(TTP) reacts with alkyl halides, acyl halides, aroyl halides, and sulfonyl halides, but it shows no evidence of reaction with molecular hydrogen. These observations further emphasize the fact that Rh(TTP) is essentially a nucleophile and it therefore reacts with those reagents RX that can oxidatively add by nucleophilic attack (34). Rh(TTP) does not react with H2, and H2 seems always to add to (P complexes via a concerted mechanism (35). It appears that Rh(TTP) has very little diradical character, i.e. it is not a good analog of a carbene (35). It is possible that this unreactivity may be associated with the stereochemistry of chelation by the macrocyclic ligand. Earlier studies on the oxidative addition reactions of Rh(I) complex with a tetraaza macrocycle revealed that the Rh(I) had strong nucleophilic properties but the activation of molecular H2 was not reported (36, 37). This possibility is supported by reports that dialkyl sulfide complexes of rhodium chloride catalyze the hydrogenation of olefins (38). 

A number of dialkyl sulfides were identified in an aquifer polluted from a waste-water tank of a chemical plant that manufactured a range of alkyl halides. This observation indicated that nucleophiles other than water and OH could be active in the environment. Sulfur is widely distributed and under reducing conditions hydrogen sulfide can be produced. This acid has a pAia of 7.0 and the bisulfide ion (HS ) would predominate at basic pH values. Laboratory studies with bromohexane demonstrated that the bisulfide ion could compete with water in substitution reactions. A reaction sequence for the production of dialkyl sulfides is as follows ... 

Reaction of alkyl halides with ammonium or alkali metal hydrogen sulfide in presence of PT catalyst. 

---