Desulfuration with triethyl phosphit

Aliphatic and aromatic sulfides undergo desulfurization with Raney nickel [673], with nickel boride [673], with lithium aluminum hydride in the presence of cupric chloride [675], with titanium dichloride [676], and with triethyl phosphite [677]. In saccharides benzylthioethers were not desulfurized but reduced to toluene and mercaptodeoxysugars using sodium in liquid ammonia [678]. This reduction has general application and replaces catalytic hydrogenolysis, which cannot be used [637]. 

Interestingly, the desulfurization is atereoepecific. Pure tit- and pure tiwu-S-butenes have been obtained in over 99% yields from tlwii respective opiBulfidea by reaction with triethyl phosphite at 105-1 Wi. Similar stereoepeeifie results have also been effected with triphcml phosphine and tributyl phosphine.3 ... 

Photochemically aided hydrogenolysis of allylic C-heteioatom bonds has anracted little interest. A few methods for debenzylation of ethers, amines and thiols, catalyzed by irradiation, have been utilized (see previous section also). An unusual desulfurization of benzyl thiol with triethyl phosphite (equation 94) in high yield, catalyzed by UV irradiation, is a useful alternative to other methods described in other parts of this chapter. 

Regarding the synthesis of tetrathiafulvalenes (TTFs), the preparation of a series of substituted naphtho-1,3-dithiole-2-thiones 150 in good yields (50-78%), from 3,4,7,8-tetrachloronaphtho[l,8-f, 5,4-fV ]bis(l,2-dithiole) 149, and an excess of sodium trithiocarbonate and alkyl halide were reported (Scheme 17) <1998EJ01577>. The monosubstitution products 151 were formed when equimolar quantities of derivatives 149 and sodium trithiocarbonate were used. Upon desulfurization with mercury(ll) acetate, the bis- and monosubstituted l,3-dithiol-3-thiones 150 and 151, respectively, yielded the corresponding l,3-dithiol-2-ones, whereby dechalogenation of 150 (R = 7-CsHii) with triethyl phosphite gave rise to the TTF 152. 

Several other metal salts have been proposed to react with acid halides to give acid anhydrides in good yield. Thus, thallium carboxylates in etheral suspension may be treated with acid halides to lead to acid anhydrides in high yield. The method has the advantage that thallium chloride can be separated by filtration and the product is isolated after evaporation of the solvent. Another synthetic possibility exists in the desulfurization of thioesters with mercury(II) carboxylates. Mercuiy(II) carboxylates can also be reacted with triethyl phosphite or tri-n-butylphosphine to provide acid anhydrides in yields of 60-80%. Another possibility is offered by the reaction of 1 mol of iV,Af-dicyclohexylthiourea and 2 mol of silver or mercury(II) carboxylates. Mixed carboxylatocarbamato anhydrides follow from the room temperature reaction of iV, -dialkylcarbamato metal derivatives with acid chlorides. Either Na, Cu", Ti" or V" are employed. ... 

Hoffmann et al. found that triethyl phosphite when heated with an aliphatic alcohol other than ethyl undergoes uncatalyzed transesteriflcation in three distinct steps which proceed at about equal rates. A mercaptan, on the other hand, is desulfurized to give the hydrocarbon and triethyl thionophosphate, both in good... 

Desulfurative alkylation and acylation. Titanocene bis(triethyl phosphite) promotes desulfurative alkylation of allylic sulfides (dithioacetals) with f-alkyl halides. ... 

One of the most versatile procedures for the olefination of carbonyl compounds utilizes a thioacetal-titanocene(II) system [40, 92]. The organotitanium species generated by the desulfurization of thioacetals with the triethyl phosphite complex of titanocene(II) 44 react with a variety of multiple bonds, such as those of alkenes [93], alkynes [94], and nitriles [95], as well as carbonyl functions. The reactivities observed in these reactions indicate that the active species involved are titanocene-alkylidene complexes 48 (Scheme 4.40). 

By phosphites and phosphines. Triethyl phosphite76 and triethyl-,18 tributyl-,38 and triphenylphosphines1 18 have been reacted with a number of episulfides to yield practically quantitative amounts of triethyl thionophosphate and trialkyl- or triiirvl phosphine sulfides, respectively, and the olefin resulting from desulfurization of the episulfide (Eqe. 54 and 55). 

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