Acidity, thioamide

The cyclization of pentaacetyl-o-gluconic thioamide with chloroacetone and of pentaacetyl-D-galactonic acid thioamide with phenacyl bromide give the corresponding 4-substituted 2-(D-galactopentaacetoxypentyl)-thiazoles (27) (660) but in low yield (23 to 27%) (Scheme 13). The products may be deacetylated in the usual way. These compounds are interesting from a pharmacological point of view. 

In the reaction of salicylic acid thioamide 419 with 2-cyano-3,3-bis(methylsulfanyl)acrylate under acidic conditions, a 2-(o-hydroxyphenyl)-6-imino-l,3-thiazine derivative was obtained as a perchlorate salt 420 on treatment with phenacyl bromide, this underwent a ring transformation to yield 4-benzoylmethylthio-27/-l,3-benzoxazin-2-ylidene-substituted ethyl cyanoacetate 421 (Scheme 81) <2003H(60)2273, 2004H(63)2319>. 

Various more or less efficient methods have been reported for the synthesis of 2-(l-ami-noalkyl)thiazole-4-carboxylic acids and their suitably protected derivatives. 237,539,541,558-568 Optimal conditions must be selected in these syntheses to prevent racemization at the chiral aminoalkyl moiety, e.g. when applying a modified Hantzsch synthesis 559 racemization has been observed to occur at the level of the starting Na-protected amino acid thioamide as well as in the base-mediated dehydration step of the intermediate hydroxydihydrothiazoles. 558 The 2-(aminoalkyl)thiazole-4-carboxylic acids are incorporated into the linear precursors by standard procedures of peptide synthesis, 237,514,529,539,552,555,558,564,569 and cyclization is pref-... 

N-Protected amino acid amides 14 react with tetraphosphorus decasulfide (P4S10) in the presence of NaF in DME at room temperature to give amino acid thioamides 15 that are... 

Many functional derivatives incorporating a thiazole ring in their structure have been produced by this method. An illustrative example is the condensation of pentaacetyl-D-galactonic acid thioamide with chloroacetone to give 4-methyl-2-(D-galactopen-taacetoxypentyl)thiazole which is deacetylated in the usual way (Scheme 164) (69ACH(62)179). 

Determinations of absolute configurations of trans-cyclopropane-l,2-dicarboxylic acids on the basis of a definite Cotton effect seem to be possible for carboxylic acid thioamides. In these molecules, such as 123a and 123b, there is a Cotton effect near 330 nm which results from the (n, n ) excitation of the thioamide chromophore . In the... 

The stable, monomeric 0-enaminodithioesters, like their thioketone counterparts, have been shown to participate in regiospecific, intermolec-ular Diels-Alder reactions with a range of representative electron-deficient and reactive dienophiles (Scheme 8-1V).19-20 Cinnamic acid thioamides exist in equilibrium with their dimers at room temperature, although to date no reports of their cycloaddition with other dienophiles have been detailed [Eq. (9)].21... 

Carboxylic acid thioamides from CONHR -> CSNHR... 

Carboxylic acid thioamides from amines s. 4, 547 CH2NH2 CSNHs... 

Carboxylic acid thioamides from COCH3 —>- GH2CSNH2... 

Aldonic acid thioamide acetates (619) condensed with various a-halo-ketones to afford the 2-(alditol-l-yl)lhiazoles 620 [54AQ(B)609, 54CB78 69ACH(62)179, 69T3413 87H947 95TL3781] (Scheme 163). 

Oxidation of C-methyl derivatives of IPs is a very important reaction for the preparation of aldehydes, carboxylic acids, thioamides and other derivatives. The... 

Carboxylic acid thioamides from carboxylic acid chlorides... 

Carboxylic acid thioamides. Ca. 2 moles AICI3 added slowly with ice-cooling to anisole and dimethylthiocarbamyl chloride, stirred at room temp., finally warmed 15 min. at 40° p-methoxy-N,N-dimethylthiobenzamide. Y 11%. F. e., also thioketones, thiono- and dithio-carboxylic acid esters, s. H. Viola, S. Scheithauer, and R. Mayer, B. 101, 3517 (1968). 

Ring closure with carboxylic acid thioamides... 

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