Heterocyclische Verbindungen, VII. Über die Reaktionsfähigkeit von Methylgruppen im Pteridinsystem

Cleavage of N-phenylpyridinium or N-vinylpyridinium salts with secondary aliphatic amines leads to aromatic amino compounds or enamines which are often unobtainable by other routes. The other fragment, glutacondialdehyde or its rnonoanil, gives azulenes, as shown by Ziegler and Hafner, as well as Konig; these compounds can also be prepared from alkylpyridinium salts with cyclopentadienylsodium (Hafner). Syntheses of labile aldehydes which are otherwise dijjjcult to obtain and of a-ketocarboxylic acids, starting from pqiridinium salts and proceeding via nitrones or a-cyanoanils, are illustrated by many wcw examples. Benzimidazoles, benzothiazoles, and amidines are accessible from pyridinium salts via nitrones or a-cyanoanils; cyanoanils can be transformed into guinoxalines (including xanthopterine), perimidines, etc. Furthermore, nitrosonaphthols and nitrosonaphthylamines react with pyridinium salts containing an active iizethylene group on the nitrogq leading to new ring syslems. Further syn fhetic possihilities arise from nucleophilic &isplacements of the pyridine in pyriditiium salts by SN2 reactions. Combination of the route via nitrones with the methods of Arndt-Eistert, Ortoleva-King, or with chloromethylation constitutes a significant enlargement of its range of'application. The forniation of a-cyanoanils from diazoketones permits synthesis of a-keto-0-umino acids from a-amino acids, or of phenylglyoxylic acids from benzoic acids by chain extension.

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“…(39) [51]. The aminopyruvaldehyde derivatives can be converted into their diethylacetals or bis(ethy1enemercaptals) [49].…”

Section: Alkmentioning

confidence: 99%