Thiobenzoic acid

Thioacids (191) react with ia -thiocyanatoacetophenone to produce 2-mercapto-4-phenylthiazole (192) (Scheme 99). With tbioacetic acid 192 is obtained directly while with thiobenzoic acid, an acyclic intermediate (193) has been isolated that is cyclized by heating with dilute acid (Scheme 100) (143). 

Pd(dba)DPPB, 2-thiobenzoic acid, THF, 70-100% yield.Tertiary allyl-amines are cleaved efficiently at 20°, but secondary allylamines require heating to 60° to achieve cleavage. Thus, it is possible to monodeallylate a diallylamine by running the cleavage at 20°. "... 

Protected 3-methyl-D-cystein (257 Scheme 3.94), a structural unit of the peptide antibiotics nisin and subtilin, has been synthesized through the ring-opening of the aziridinecarbamide 254 with thiobenzoic acid (255) [143, 144]. The reaction took place overnight at room temperature and in methylene chloride to give 256 in greater than 95% yield. 

Thiobenzoic acid, 32,101 Thiocarbonyl perchloride, 32, 69 Thiolacetic acid, 31,105... 

However, the switchover from an A2 to an A1 hydrolysis is a very common mechanistic pathway in strong acid media, probably more common than the pure A2 mechanism. Excess acidity analyses have shown that thioacetic acid, several thiobenzoic acids, and many thiolbenzoate and thionbenzoate esters show this sort of mechanism switch.179 Acylals and thioacylals also show this behavior,116 with thioacylals using two water molecules and acylals one. Many hydroxamic acids react this way,127,216 as do esters of various types,41,217,218 episulfoxides219 and aryloxatriazoles.220 Acylhydrazines can also show a mechanism switch of this sort, although with these substrates the situation is somewhat more complex.221... 

The synthesis of four out of eight possible stereoisomers of 3-methyllanthionine [(25,35,67 ), (25,37 ,67 ), (25,35,65), (25,37 ,65)] has been achieved using the reaction of Z-protected 3-methyl-D-cysteine with d- or L-3-chloroalanine in yields of 35—53% J64 The methyl-D-cys-teine stereoisomers were obtained by two routes. Firstly from (25,35)-threonine via O-tosylation and subsequent inversion of configuration by nucleophilic attack with thiobenzoic acid. The resulting derivative was debenzoylated and oxidized to the respective cystine derivative prior to the reduction with Zn/HCl to give the eryt/u-o-3-methyl-D-cysteine... 

Cleavage of allylamines is rather difficult. However, unexpectedly the allylamine 340 is deprotected by allyl transfer to dimethylbarbiturate (341) [158] or to 2-thiobenzoic acid using DPPB as a ligand [159]. The 2-thiobenzoic acid method has been applied to indole synthesis [160], Allylamines are also cleaved with Pd/C in EtOH in the presence of methanesulfonic acid [161] or with Ni(dppp)Cl2 [162], Thus diallylamine (339) can be regarded as protected ammonia. 

Thiobenzoic acid Potassium t-butoxide 1-Benzoyl glycerol Cytosine... 

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