The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Stereochemical studies. XXIV. Stereoisomeric (benzoylmercapto)succinic and (benzoylmercapto)succinamic acids》. Authors are Holmberg, Bror.The article about the compound:(S)-2-Bromosuccinic acidcas:20859-23-8,SMILESS:O=C(O)[C@@H](Br)CC(O)=O).HPLC of Formula: 20859-23-8. Through the article, more information about this compound (cas:20859-23-8) is conveyed.
cf. C.A. 35, 5465.3. BzSH (6.9 g.) and 5.8 g. maleic acid in hot AcOH yield 7.6 g. DL-HCO2CH(SBz)CH2CO2H (I), m. 177-82°. L(-)-HCO2CH(SBz)CH2CO2H, sintering 175° and m. 182-3°, [α]D20 -6°, [α]D20 -123° (c 0.5028, Me2CO), [M]D20 -315°, was prepared from BzSH, Na2CO3, and L(-)-CHBr(CO2H)CH2CO2H (II) in H2O, while the D(+)-isomer (III), m. 176-80°, [α]D20 6°, [α]D20 124° (c 0.5028, Me2CO), [M]D20 315°, results from the same starting materials when alc.-H2O, and no Na2CO3 is used. III with concentrated NH4OH yields BzNH2 and some dithiodimalic acid, m. 164-6°, [α]D20 257° (Me2CO). PhCSNH2 and II in EtOAc yield PhC(NH2Br)SCH(CO2H)CH2CO2H, m. 205°, with foaming; this in turn is converted by heating in H2O to S.CPh:N.CO.CHCH2CO2H, m. 195-7°. From DL-NH2COCHICH2CO2H with Na2CO3 and BzSH in H2O was prepared DL-BzSCH(CO2H)CH2CONH2, m. 174-5°, while the D(+)-isomer (IV), m. 164-5°, [α]D20 105°, [M]D20 266°, was prepared from L(-)-NH2COCHBrCH2CO2H and BzSK in Na2CO3 solution The free acid, HSCH(CO2H)CH2CONH2 m. 115-16°, [α]D20 84° (c 0.4, Me2CO), was prepared by treating IV with concentrated NH4OH, distilling in vacuo, and acidifying with H2SO4. The course of these reactions may be explained by the mechanisms proposed by Fredga (The Svedberg-Buch 1944, p. 261).
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Reference:
Copper catalysis in organic synthesis – NCBI,
Special Issue “Fundamentals and Applications of Copper-Based Catalysts”