Homolytic acylation of protonated pyridines and pyrazines with .alpha.-keto acids: the problem of monoacylation
摘要:
The silver-catalyzed decarboxylation of alpha-keto acids by persulfate leads to acyl radicals, which can effect the selective homolytic acylation of pyridine and pyrazine derivatives. Compared with the previously developed source of acyl radicals by hydrogen abstraction from aldehydes, this procedure is more effective in monoacylation when multiple positions of high nucleophilic reactivity are available in the heterocyclic ring. Although the introduction of an acyl group strongly activates the heterocyclic ring toward further substitution, monoacylation can be achieved by taking advantage of the difference in basicity and lipophilicity between the starting base and the monoacylation products in a two-phase system.
Verbindungen der Formel I
worin A, X₁, X₂, X₃, X₄, Y, Z und R₁-R₆ die in der Beschreibung angegebenen Bedeutungen haben, weisen wertvolle pharmazeutische Eigenschaften auf und sind insbesondere gegen Tumoren wirksam. Sie werden in an sich bekannter Weise hergestellt.
式 I 的化合物
其中 A、X₁、X₂、X₃、X₄、Y、Z 和 R₁-R₆ 具有描述中给出的含义,具有宝贵的药用特性,对肿瘤特别有效。它们以已知的方式生产。
FONTANA, FRANCESCA;MINISCI, FRANCESCO;BARBOSA, MARIA CLAUDIA NOGUEIRA;VIS+, J. ORG. CHEM., 56,(1991) N, C. 2866-2869
作者:FONTANA, FRANCESCA、MINISCI, FRANCESCO、BARBOSA, MARIA CLAUDIA NOGUEIRA、VIS+