Thioamides, synthesis

Another frequently used multicomponent reaction is the Kindler thioamide synthesis (the condensation of an aldehyde, an amine, and sulfur). The Kappe group has described a microwave-assisted protocol utilizing a diverse selection of 13 aldehyde and 12 amine precursors in the construction of a representative 34-member library of substituted thioamides (Scheme 6.114) [226]. The three-component con-... 

On the other hand, thiocarbamoyl chlorides (15) may be used in thioamide synthesis, though via carbon-carbon bond formation in Friedel-Crafts-type reactions (c/. Volume 2, Chapter 3.1). The approach is limited to fairly electron-rich aromatics such as alkylbenzenes, anisole, and furan, but fails for benzene equation (7) gives some details. - Phenol does not require a Lewis acid catalyst in the reaction with H CSCl, but gives a mixture of 2-/4-hydroxythiobenzamides along with O-phenyl thiocarba-mate. ... 

Another application of thiocarbamoyl chlorides (15) and related activated thiocarbonic acid derivatives in thioamide synthesis is found in their reaction with carbanions of highly CH acidic compounds EWG2CH2 to give thioamides EWG2CHCSNR2. ... 

Thioamide synthesis from dithiocarboxylates and amines under basic conditions gives thiols as rather unpleasant parallel products. This problem is avoided by using S-thioacylated thioglycolic acids (17), as... 

Thioketenes (34) are highly electrophilic and give a smooth reaction with ammonia or amines. In fact, addition of a secondary amine offers the best way to scavenge a suspected thioketene. But the approach also deserves interest from the point of view of thioamide synthesis as it allows very mild and nonreducing conditions, tolerating the presence of sensitive additional functional groups such as cyano, nitro, or sulfonyl residues (equation... 

The most common source of imidates is nitriles (c/. Volume 6, Chapter 2.7) and, as these can be directly transformed into thioamides (c/. Section 2.4.3.4), this one-step approach is usually preferred. Moreover, depending on the reaction conditions and the substitution pattern, thiolysis of imidates may give thioesters rather than thioamides (c/. Volume 6, Chapter 2.5). However, some high-yield applications of imidates in thioamide synthesis have been reported and are detailed in equations (27) ° and (28). ... 

---