Thioates

Recently Oldenziel and Van Leusen (750) have reported a new synthesis of 4-tosylthiazoles (275), R = p-MeOCgH4, p-MeCgH, Ph, p-ClCgH, and 2-furyl, from tosylisocyanide (272) and carboxymethyldi-thioates (273) (Scheme 142) yields ranged from 50 to 80%. 

The acid chlorides are generally more reactive than the corresponding acid anhydrides. In fact, the alcoholysis of acid chlorides is probably the best laboratory method for preparing esters. Frequentiy, basic materials are added during the course of the reaction to neutralize by-product hydrochloric acid. When the basic material is aqueous caustic, the procedure is referred to as the Schotten-Baumann procedure (73). Esterification of tertiary alcohols by acid chlorides is described in Reference 74. Esters of tertiary alcohols can also be formed through an intermediate /-butyl thioate group (75) ... 

AgOAc (Pyr, H2O) cleaves both thioates of 1 to give a phosphate." ... 

Thioesters are named like the corresponding esters. If the related ester has a common name, the prefix thio- is added to the name of the carboxylate acetate becomes thioacetate, for instance. If the related ester has a systematic name, the -oate or -carboxylate ending is replaced by -thioate or -carbothioate butanoate becomes butanelhioate and cyclohexanecarboxylate becomes cyclohexane-carbothioate, for instance. 

Pyrolysis of the phosphorodichloridothioate (59) at 550 °C gives mainly dibenzothiophen and a smaller amount of the cyclic phosphonochlorido-thioate (60). Thermal decomposition of di-t-butyl peroxide in triethyl phosphate gives rise to diethyl methyl phosphate in a reaction which may be interpreted as resulting from attack of methyl radical on the phosphoryl oxygen. An extension of this mechanism accounts for the formation of (61) from tri-isopropyl phosphate under the same conditions. 

Degradation of the insecticide chlorpyrifos has been examined in solutions of aqueous chlorine in which the primary oxidant is hypochlorous acid/hypochlorite. The final product was 2,3,5-trichloropyrid-2-one produced either directly, or via initial oxidative conversion of the thioate ester by replacement of the sulfur with oxygen (Duirk and Collette 2006). An analogous oxidation was found with diazinon (Zhang and Pehkonen 1999). 

C16H16N608PS C6H16N Adenosine 5,-(triethylammonium phosphoro-thioate), p-nitrophenyl ester (sp diastereoisomer) (EADNPP)177... 

A kinetic isotope effect 160/180 of 2% in the spontaneous hydrolysis of the 2,4-dinitrophenyl phosphate dianion, whose ester oxygen is labeled, suggests a P/O bond cleavage in the transition state of the reaction, and thus also constitutes compelling evidence for formation of the metaphosphate 66,67). The hydrolysis behavior of some phosphoro-thioates (110) is entirely analogous 68). 

Tolkmith, H., Aromatic phosphorodichloridites and phosphorodichlorido-thioates. I. Aryl phosphorodichloridites, /. Org. Chem., 23, 1682, 1958. 

Table 8 Computed second-order rate constants (k2n) for the La2 + COCH3) -catalyzed methanolysis of paraoxon 1 and its thioate derivative 3 obtained through fits of k2bs at each (pH to Equation (8)a...

Because anti/syn ratios in the product can be correlated to the E(0)/Z(0) ratio of the involved boron enolate mixture,10b initial experiments were aimed at the preparation of highly E(0)-enriched boron enolate. The E(0)/Z(0) ratio increases with the bulk of the alkanethiol moiety, whereas the formation of Z(O) enolates prevails with (S )-aryl thioates. (E/Z = 7 93 for benzenethiol and 5 95 for 2-naphthalene thiol esters). E(O) reagent can be formed almost exclusively by reaction of (5)-3,3-diethyl-3-pentyl propanethioate 64 with the chiral boron triflate. High reactivity toward aldehydes can be retained in spite of the apparent steric demand (Scheme 3-22).43... 

This section is concerned mostly with the enzymatic hydrolysis of substrates classified as phosphoric acid mono-, di-, and triesters, phosphonates, phosphoro(di)thioates, phosphonodithioates, and P-halide compounds. 

Meikle, R.W. and Youngson, C.R. The hydrolysis rate of chlorpyrifos, 0,0-diethyl 0-(3,5,6-trichloro-2-pyridyl) phosphoro-thioate, and its dimethyl analog, chloropyrifos-methyl in dilute aqueous solution, Arch. Environ. Contam. Toxicol,... 

An illustration of the use of -methyl-substituted thioesters in the synthesis of natural products is present in the total synthesis of a /3-D-mannosyl phosphomycoketide from Mycobacterium tuberculosis (Figure 5). Addition of MeMgBr to ethyl 6-benzyloxy-2-hexene thioate catalyzed by Cu/Josiphos (92% yield, 93% ee) furnished one of the building blocks. The other four methyl groups were introduced using copper/phosphoramidite-catalyzed dimethylzinc addition. 

Diaryl ketones.2 In the presence of this complex (1 equivalent) S-(2-pyridyl) aryl thioates (1 equivalent), prepared from aryl carboxylic acids, undergo reductive homocoupling to diaryl ketones (equation I). 

Although the unusual dimerized phosphorohydrazide thioate 468 was isolated from the marine fungus Lignincola laevis, it was postulated that this compound is a biotransformation product of an insecticide that was present in the seawater. However, attempts to locate a comparable structure through the chemical registry have been unsuccessful. This compound showed cytotoxicity against L1210 cell line at a level of 0.25 pg/ml level [358]. 

O-p-Nitrophenyl thiophosphate No cleavage S-Phosphoro-thioate, p-nitro-phenol... 

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