Thioamides desulfurization

Conversion of thioamides by desulfurization into the corresponding amides has been reported (Scheme 32). 

Desulfurization of phosphonylated thioamides has been achieved by nickel boride.71 73... 

A novel route to synthesize l,3 -triazine-2,4(l//,3//)-diones through the desulfurization of thiocarboamides, such as 1,3-disubstituted 2-thioureas, trisubstituted thioureas and N-substituted thioamides by silver cyanate has been reported <00H(53)929>. Treatment of urazole 23 with one equivalent of sodium hydride under anhydrous conditions, followed by addition of dimethyl sulfate, leads to l,3,5-triazine-2,4-dione 24 in 80% yield . 

Kappe has recently published a modified desulfurative cross-coupling method, using a direct reaction on thioamides under microwave assistance.123,124 It was shown that, in contrast to cross-coupling alkylsulfanyl-iV-heteroaromatics and boronic acids, 2 to 3 equivalents of CuTc cofactor were needed to achieve high yielding conversions (Scheme 64). 

Thioamides were converted to aldehydes by cautious desulfurization with Raney nickel [1137, 1138] or by treatment with iron and acetic acid [172]. More intensive desulfurization with Raney nickel [1139], electroreduction [172], and reduction with lithium aluminum hydride [1138], with sodium borohydride [1140] or with sodium cyanoborohydride [1140] gave amines in good to excellent yields. 

Oxidative desulfurization of the thiourea moiety is known to occur by an in vivo metabolism which forms the corresponding carbonyl compound, although there is no direct evidence for involvement of any activated oxygen species like superoxide, which is distributed widely in living cells. It was found that various thiocarbonyl derivatives such as thioureas, thioamides and thiocarbamates were readily desulfurized with 51 to the corresponding carbonyl compounds in almost quantitative yields at —35°C in CH3CN (equation 82). Desulfurization of thiourea with 02 was previously reported but the yields were comparatively low. ... 

Diphenylphosphinic chloride reacts with the superoxide anion radical (Oi ) in CH3CN under mild conditions to form the diphenylphosphinic peroxy radical intermediate 77, which shows strong oxidizing abilities in the epoxidation of alkenes, oxidation of sulfoxides to sulfones, desulfurization of thioamides to amides and oxidation of triphenylphos-phines to triphenylphosphine oxide in good to excellent yields (equation 105). ... 

A peroxyphosphorus intermediate 79 or 80 generated from phenylphosphinic dichloride and superoxide at —4°C desulfurizes thioamides to amides in excellent yields (equation 106)2. ... 

Desulfuration.1 The reaction of K02 with o-nitrobenzenesulfonyl chloride results in a peroxysulfur reagent that converts thioureas, thioamides, and thiocar-bamates in CH3CN at -30° into the corresponding carbonyl compounds. Example ... 

Desulfuration.4 Thioureas and thioamides are converted into ureas and amides in 60 80% yield by reaction with KOz crown ether in DMF at 25°. lixamples ... 

Oxidative desulfuration of thiomides.1 The reaction of these two reagents generates a peroxyphosphonic intermediate that converts thioamides into the corresponding amides in 90-95 % yield via a sulfine intermediate. 

Desulfuration.1 Thioamides are known to be converted into amides by potassium superoxide (13, 260). The reagent can also effect cyclodesulfuration in the case of N-(2-hydroxyphenyl)thioamides to provide benzoxazoles in generally high yield. 

Due to the ease of preparation of thioamides (c/. Chapter 2.4. of this volume) there is considerable interest in the desulfurization of these to the corresponding amides (equation 31). 

Thioamides of two cyclopropanecarboxylic acids undergo coupling reactions with diazomethane derivatives in refluxing benzene containing rhodium(II) acetate. The reaction conceivably takes place via a thiirane intermediate which undergoes reductive elimination by reaction with excess diazo compound. An example of an intramolecular reaction is the formation of indolizine 2. If the diazo compound is not in excess a thiol is formed, this can be removed by Raney nickel desulfurization. ... 

Use Dehairing hides desulfurizing viscose rayon in the manuf of sulfur -contg dyes and other thio compds such as thioamides. thiourea, thioglycolic acid, thio- and dithioben-zoic acids, sodium thiosulfate. 

Sulfides are oxidized to sulfoxides. C Tioval of a benzylthioethyl group from makes the group base-labile. When the si ears chiral ligands, the oxidation becom< Cyclic thioamides are desulfurized to i C=N — C=0. Ketoximes, hydra onyl products. 

Desulfurization. Thioketones and thioamides are converted by this reagent in refluxing DME into hydrocarbons and amines, respectively. ... 

Desulfurization. Iron carbonyl in the presence of potassium hydroxide forms potassium hydridotetracarbonyl ferrate, K HFe(CO)4 (1). This hydride converts thioketones and thioamides to hydrocarbons and amines, respectively, in 50-807o yields. 

Details of the diastereoselective synthesis of the bicyclic thietane (33) by solid-state photocyclization of an acyclic thioamide are available (94JOC3131). Photocycloaddition of 1,1-diphenyl-ethene to 4-thioazetidin-2-one gives the adduct (34) which, on desulfurization, provides a route to 4-spirocyclopropyl -lactams (93TL5951)(see 4.7). 

---