A variety of vinylogous iminium salt derivatives have been examined as useful precursors for the regiocontrolled synthesis of heterocyclic appended pyrazoles. The reaction conditions for such processes have been optimized and the regiochemical preferences have been determined. Such reaction sequences represent methodologies which may have useful applications for the preparation of biologically interesting substances.

Reactions of 2,3-disubstituted chloropropeniminium salts and related synthons with ethyl glycinate, ethyl N-methylglycinate, and ethyl N-benzylglycinate have been studied tinder acidic, basic and neutral conditions. Such reactions have resulted in efficient and selective methodology for the synthesis of unsymmetrical 2,3,4-trisubstituted pyrrole systems. (C) 1998 Elsevier Science Ltd. All rights reserved.

The synthesis of heterocyclic appended vinylogous iminium salts is described along with their conversion to heterocyclic appended pyrimidines, triazolopyrimidines, and pyrroles.

The reaction of 1-substituted vinamidinium salts with sarcosine ethyl ester produced 2,3-disubstituted pyrroles; a similar reaction with glycine ethyl ester gave 2,5-disubstituted pyrroles. Reactions of related three-carbon synthons with sarcosine and glycine were studied under basic, neutral and acidic conditions which demonstrated the utility of these derivatives for the regiocontrolled preparation of disubstituted pyrroles.

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The reaction of unsymmetrical vinylogous iminum salts and related analogs with β-aminocrotononitrile to yield 2,3,6-trisubstituted pyridines with regioselective control is described.

The reaction of a 2-(1-benzotriazolyl)vinamidinium salt with Grignard reagents to yield alpha,beta-unsaturated aldehydes with stereochemical control is described.

The synthesis of two, vinylogous iminium salts, which contain an appended thiophene group, are described along with their conversion to thiophene substituted pyrimidines and pyrroles.

The reaction of vinylogous iminium salts and related analogs with 3-amino-1,2,4-triazole to yield 7-substituted and 5-substituted triazolo [1,5-a]pyrimidines is described.

A three step synthesis of a novel 2-(1-benzotriazolyl)-vinamidinium salt is described along with its direct conversion to a series of unusual 5-(1-benzotriazolyl)pyrimidines, 4-(1-benzotriazolyl)-pyrazoles, and 4-(1-benzotriazolyl)pyrroles.