Thioacrylic acid

Mixtures of isomers were obtained from the reaction of cis- and trans-a-bromocinnamic acid with arylthiolate ions (Angeletti and Montanari, 1958). The corresponding m- and p-nitro acids reacted faster but gave complete retention. The slower reaction of the unsubstituted acids was probably followed by isomerization of the product, since j9-thioacrylic acids isomerize in similar media (Montanari, 1960). 

Oxidative cyclization of 3-amino-thioacrylic acid-amides, -esters or 2-amino-l-alkenyl-thioke tones ... 

Oxidative Cyclization of 3-Amino-Thioacrylic Acid-Amides, -Esters or 2-Amino-l-A Ikenyl- Thioketones... 

The oxidation of N-monosubstituted 3-amino-2-aryl-thioacrylic acid-morpholides 20 using hydrogen peroxide in perchloric acid gave 5-morpholino-isothiazolium perchlorates2 21a,c-g (83JPR689) in good yields (Scheme 4). The electrochemical oxidation of 3-amino-thioacryl acid-amides 20 (R = CH2C02Me) is a useful... 

Furthermore, isothiazolium salts are masked enaminothioketones and thioacrylic acid derivatives, which can be obtained by reductive ring cleavage. 

The a-addition of alkyl or aryl thionucleophiles R H to y9-nitroacrylates R2(NC>2) C=CC02R3 in THF in the presence of Et3N or DBU does not stop at y9-nitro-o -thioalkanoates R2CH(N02)CH(SR1)C02R3, but proceeds further with concomitant elimination of nitrous acid to afford a-thioacrylates R2CH=C(SR1)C02R3.191... 

DCC can be used to prepare 5-alkyl and 5-aryl thiocarboxylates (1) from carboxylic acids and thiols according to equation (5). This method has been successfully applied to the synAesis of thiol esters with sensitive substituents, e.g. 5-methyl thioacrylate, a natural product. In particular, N-protected amino acid and peptide 5-phenyl esters, which are useful building blocks in peptide synthesis, are obtained in excellent yields without racemization. N-Hydroxyphthalimide and DMAP have been used as cocatalysts to facilitate the reaction. The preparation of the Wittig reagent (5) by this route is shown in equation (6). 

Since thiols and thiyl radicals are known to readily undergo addition reactions at unsaturated carbon centers (199, 202, 204), a possible mechanism for this inactivation reaction is shown in Scheme 43. Addition of the active site nucleophilic or radical species followed by protonation or electron transfer, respectively, would yield the thioacrylate derivative and inactive enzyme. Of course, addition to C-2 of propargylic acid is also possible, forming a 2-substituted acrylate derivative instead. 

---