Thiocarboxylic acids, acidity

Mercapto Exist largely in the thione form Thiocarboxylic acid... 

S-Alkylation of a thiocarboxylic acid with an a-halogenated carbonyl compound gives a thiol ester in which the two carbons to be connected... 

Lewis TA, A Paszczynski, SW Gordon-Wylie, S Jeedigunta, C-H Lee, RL Crawford (2001) Carbon tetrachloride dechlorination by the bacterial transition metal chelator pyridine,2,6-bis(thiocarboxylic acid). Environ Sci Technol 35 552-559. 

In the absence of electron-withdrawing ligands, disilanes possess only a little Lewis acidity consequently, they show a limited propensity to form hypervalent complexes. Starting from the symmetric methylchlorodisilanes ClMe2SiSiMe2Cl and Cl2MeSiSiMeCl2 as well as carboxylic acids and thiocarboxylic acids, Kawashima et al. have prepared rare examples of penta- and hexacoordinated disilene, namely compounds 886-889 (Scheme 125).855 856... 

Mercapto - Exists ca. 99.99% in pyridthione-form Compare with thiocarboxylic acid... 

S,3R). Secondly, the t/treo-3-methyl-D-cysteine (25,35) was prepared using the previously described addition of thiocarboxylic acid to threonine-derived aziridines. 62 ... 

No aminothiophenones can be obtained by photorearrangement of JV-aryl amides of thiocarboxylic acids. The formation of 2-ethoxybenzthiazole (143) by oxidative photodehydrogenation of 142 is of some interest.11 Similarly, 2-phenylbenzthiazole originates by photocyclization of thiobenzanilide in the presence of oxygen."... 

Red or blue, variously hydrated chromium(II) complexes of thiocarboxylic acids, e.g. S[(CH2)2SCH2C02H]2, have been isolated, and the red complexes are antiferromagnetic.205 Some antiferromagnetic complexes of adenine may have binuclear structures (Table 16). 

The only other thiocarboxylic acid examined thus far in this reaction has been thiobenaoio acid, reported by Nylen and Otoeo1740 to give only a poor yield of /J-bydroxyetbyl thioben2oate on addition t > ethylene oxide. 

Figure 3.14. Benzhydrylthiol-based linker for thiocarboxylic acids [194,196].

In this method, the cyclic peptide is generated through cysteine-perthioester cyclization to afford a Xaa-Cys bond whose thiol is then used for the second ligation step to the core through a thiol addition reaction (Scheme 25).[S71 For the perthioester cyclization, the linear precursor 91 consists of an activated N-terminal Cys(Npys) and a C-terminal thiocarboxylic acid which favors cyclization due to intramolecular mixed disulfide formation between them. 

The linear precursor 91 of the cyclic peptide 86b was synthesized on a thiol benzhydryl resin 88 using the Boc chemistry protocol as described in Section 14.1.6.5 the assembly was capped at the amino-terminus with Boc-Cys(Npys), cleaved, and deprotected by HF to afford the peptide thiocarboxylic acid 91. Cyclization was initiated immediately after HF cleavage in 25% MeCN in H20 containing 0.05% TFA (pH 2), giving a final concentration of 1.75 mM. The progress of the cyclization was monitored by RP-HPLC and completed in 1 h. The pH of the soln was adjusted to 6 with solid NaOAc after 10 min, DTT or TCEP was added (1-3 equiv) to the soln to reduce the hydrodisulfide 92 to afford the cyclic peptide 86b with a Cys-Gly bond the progress was again monitored and then the product was purified by RP-HPLC overall yield 36%. The characterization of 86b is similar to those described in Section 14.1.6.5. 

Tominaga et al.1B0 studied the cycloaddition of DMAD to 3-indoledi-thiocarboxylic acid derivatives (278). A 2-substituent was essential for success, and 278 (R1 = R2 = R3 = Me) gave a 90% yield of 279. Similarly, morpholino- and piperidinothioamides 282 formed cycloadducts 283. Treatment of 279 with methanolic hydrochloric acid gave 281 via the ring-cleaved intermediate 280. 

Studies of metal ion promotion of the reactions of thiocarboxylic acids and anhydrides,363 thioamides368"370 and a variety of other sulfur compounds have been carried out. The interested reader should consult the comprehensive review by Satchell.17... 

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