O-Aminocarboxylic

Hanbold et al. (83PHA269) prepared 2-arylthieno[2,3-d]pyrimidin-4(3//)-ones 19a by treating o-aminocarboxylates 1 with imidates in a mixture of chlorobenzene and PPA. 

The reactions with formation of polymers also are classified based on another difference in their mechanism. This classification distinguishes step reactions and chain reactions. In step reactions the polymers are built from the monomer by random individual reactions to form dimers, trimers, tetramers, etc., each resulting molecule being able to participate in a subsequent reaction with a monomer or with an oligomer molecule. This type of reaction may start with molecules having two reactive functional groups in one molecule such as an o-aminocarboxylic acid. Another possibility consists of reactions between two different types of bifunctional molecules such as a diamine and a dicarboxylic acid as shown below ... 

Because o-aminocarboxylic adds and their esters lack the nitrogen atom of the o-aminoamides, fewer reagents are available for thdr cyclization. 

N-Condensed heterocyclics from o-aminocarboxylic acid amides... 

Pyrimidin-4-one ring from o-aminocarboxylic acids via l,3-oxazin-6-one ring... 

Polycondensation is easier with amino carboxylic esters, since the —COOR-group is less resonance-stabilized (cf. nylon 7 and nylon 11). Even less stable, and therefore very reactive, is the acyl chloride group. However, the acyl chloride of the a,o)-aminocarboxylic acids is not easy to handle (purify, etc.), and it is not easy to control polymer formation. 

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