Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Stable Tetraazafulvalenes - Syntheses and ChemistryThe syntheses, properties and reactions are described for 1,3,6,7-tetrakis[arylamino]-1,4,5,8-tetraazafulvalenes and their vinylogous derivatives. First, the acylation of form- as well as acetamidine with bis-imidoylchlorides derived from oxalic acid 6 formed reactive cyclic intermediates which dimerized to tetraazafulvalenes 12 or bisvinylogous tetraazafulvalenes 14. Based on, a further synthesis was found using a cycloacylation reaction of amidines with imidoylchlorides 6 followed by prototropic migration of α-hydrogen. Thus, the vinylogous compound 15 and the phenylogous derivatives 16, 17 could be isolated in moderate up to good yields. Besides amidines, other derivatives of carboxylic acids as amides or thioamides could be transformed into corresponding tetraazafulvalenes 18-20. Due to their vicinal amino groups, alkylation and acylation reactions were studied. For example, the reaction with orthoformates yielded the ring fused products 24a,b which may be starting material for carbenes just as the cyclization product with thiophosgene 27. Treatment of tetraazafulvalenes with anhydrous iron-II salts or molybdenum hexacarbonyl yielded the deeply colored metal diazadiene complexes 33 and 34. Finally, reduction using metallic lithium and subsequent alkylation constitutes a convenient synthetic entry to heterocyclic analogues of stilbene 37.
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