Thiocarbonic acid derivatives

Fig. 1.37. Cyclization-free defunctionalization of the thiocarbonic acid derivative from Figure 1.35.

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. ... 

Carbon disulfide is a valuable synthon (see Chapter 9, p. 147) which can be used for the synthesis of thiocarbonic acid derivatives. Thus, carbon disulfide reacts with ammonium polysulfide or hydrogen sulfide to give trithiocarbonic acid (70) or symmetrical esters (73) after reaction with an alkyl halide. With alkoxides or thiolates, carbon disulfide forms xanthates (77) or S-alkyl trithiocarbonates the latter by further treatment with alkyl, acyl or diazonium halides affords the derivatives (74)-(76) (Scheme 39). 

Carbon disulfide is a useful synthon for the preparation of thiocarbonic acid derivatives (see Chapter 8, p. 135). Carbon disulfide will react with alkynes (18) under forcing conditions the reaction is facilitated by the presence of electron-... 

Replacement of halogen leads to formation of a C-S bond in many cases when alkyl or aryl halides are allowed to react with thiocarbonic acid derivatives such-as thiocarbamates, thiourea, dithiocarbamates, or xanthates. The importance of this method is due to the fact that the intermediates are readily converted into thiols by hydrolysis ... 

This Section consists of a review of the most important methods of preparing thiocarbonic acid derivatives. The space available suffices for details of the processes in only a few cases, and for others the literature cited must be consulted. 

The Schiff bases (18) are metallated under kinetically controlled conditions to give mostly the enamines (19), whereas under thermodynamic conditions the corresponding Z-isomers predominate. The thiocarbonic acid derivatives (20, R = CHaPh, R = Et) react with electrophiles at the a-position, after metalla-tion however, for (20, R=H or Ph) metallation and alkylation take place exclusively at the R group. This latter sequence has been used for the preparation of the oxathiolanes (21) from ketones [R R C(O)] and (20, R = R = Me). ... 

Thioureas have also been synthesized by aminolysis of other thiocarbonic acid derivatives. Carbon disulphide reacted with guanidines to yield RNHC(S)NH2 along with 1,3,5-thiadiazines (14). The tricyclic compound (15) was formed by... 

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