Vinylogous carboxylic amides

Vinylogs (Vinylogous) s. azolides, vinylogous carboxylic acid amides, -Dieckmann cyclization, -l,2-dithiole-3-thiones, -urethans, -... 

Reactions with vinylogous carboxylic acid amides Chloral condensation... 

Fluoroborates Vinylogous amidinium salts from vinylogous carboxylic acid amides and alkoxyaminomethinium salts... 

Enamines from thioimino-esters. - Vinylogous carboxylic acid amides. Startg. thioimino-ester dissolved in triethyl phosphite, and warmed 20 hrs. at 60° under Ng -> product. 

Synthesis of a,/ -ethyleneketones from vinylogous carboxylic acid amides... 

If vinylogous imidazole-A-carboxylates (route A) are treated with nucleophiles such as alkoxides or amines, the corresponding vinylogous carbonic esters or amides are obtained. While reaction of the vinylogous imidazole-TV-carboxylate with a thiol (route A) yields the addition product only, that of the corresponding imidazolium compound (route B) leads to the carbonic thioester in a substitution reaction [3]... 

Finally, by placing the additional carbonyl in the carboxylic component, a synthesis of pyridinones 131 has been realized [115]. In this case, the nucleophilic carbon is not the one derived from the acid, but the one initially embedded in the starting aldehyde. Moreover, here a vinylogous Knoevenagel is operating, which is clearly favoured over the reaction involving the carbon a to the amide, thanks to the formation of a stable aromatic 6-membered ring. 

By analogy with cyclopropanes and oxiranes, 2-acylaziridines, aziridine-2-carboxylic esters and amides, are also suitable substrates for one-electron reductive ring cleavage. This is an efficient and highly regioselective method for the synthesis of yS-amino carbonyl compounds. Vinylogous substrates are, furthermore, transformed into <5-amino y8,y-unsaturated carbonyl derivatives azetidines can also be used to achieve y-amino functionalization (Scheme 19) [72]. 

As work progressed, we desired an acid intermediate that would allow us a broader spectrum of structural variants on the amide nitrogen. We found that the desired vinylogous carbamic acid could be prepared directly from cyanoacetic acid (Figure 5). When R equals (substituted)benzyl, an approximate 1 1 ratio of desired products and decarboxylated products was obtained. When R equals (substituted)phenyl, only the desired carboxylic acid intermediates were obtained. The impure vinylogous carbamic acids could easily be purified by base extraction. These acids were converted to vinylogous ureas via their stable acid chlorides. 

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