A-Mercaptocarboxylic acid

More extensive studies have shown that a-mercaptocarboxylic acids, ethyl nitrite, and iVJV -dicyclohexylcarbodiimide with a catalytic amount of sulfuric acid yield meso-ionic l,3,2-oxathiazole-5-ones (169), presumably via intermediate 5-nitroso derivatives (170). 

The reaction of a -mercaptocarboxylic acids (347) with dicyanogen affords good yields of 4,4 -dioxo-2-bithiazolinyl (349 Scheme 222) (69JOC2053). 

Dioxathiolan-4-one 2-oxides (50) decompose rapidly in the presence of water and mineral acids to form a-hydroxy carboxylic acids, the detailed mechanism of hydrolysis being unknown. Nucleophilic attack on (50) by alcohols occurs at the acyl carbon atom and, with elimination of sulfur dioxide, gives a-hydroxy carboxylic acid esters (76CRV747). In a similar fashion to (50), l,2,3-oxadithiolan-5-one 2-oxides react rapidly with water to yield the parent a-mercaptocarboxylic acids (77MI43301). 

Comprehensive review chapters on 1,3-oxathiolium salts <02MI35> and 1,3-oxaselenolium salts <02MI93> have appeared. Scandium triflate has been introduced as an efficient catalyst for reaction of aldehydes with mercaptoethanol to form 2-substitued 1,3-oxathiolanes <03S2503>. Protection of a-mercaptocarboxylic acids is readily achieved by... 

A library of spiro[indole-thiazolidinones] (158) was prepared sonochemically by a three-component reaction in an aqueous medium in the presence of cetyltrimethyl-ammonium bromide (CTAB) as a phase-transfer catalyst (Dandia et al. 2011b). The reaction of isatins (155), aryl or heteroaryl amines (156), and a-mercaptocarboxylic acids (157) under ultrasound for 40-50 min afforded the target molecules in good to excellent yields (80%-98%) (Scheme 8.51). 

From Enamines and Mercaptocarboxylic Acids. In the course of their wider study of the reaction between enamines and thiol adds, Klemmensen et have described a smooth condensation of enamines (312) derived from ethyl acetoacetate and ammonia or methylamine (/.e. ethyl j8-amino-crotonates) with a-mercaptocarboxylic acids (311) to thiazolidinones (313). The cyclization involves the addition of the thiol group, of (311), to the double bond, and amide formation between the amine and acid. ... 

Dicyclohexylcarbodiimide sulfuric acid 5-Hydroxy-l,3,2-oxathiazolium betaines from a-mercaptocarboxylic acids... 

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