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Sites of protonation in cardiotonic polyazaindolizines by NMR spectroscopy

 

作者: Paul Barraclough,   David Firmin,   John C. Lindon,   Malcolm S. Nobbs,   Paul N. Sanderson,   Steven Smith,   Janet M. Gillam,  

 

期刊: Magnetic Resonance in Chemistry  （WILEY Available online 1991）
卷期: Volume 29, issue 5  

页码: 468-475

 

ISSN:0749-1581

 

年代: 1991

 

DOI:10.1002/mrc.1260290511

 

出版商: John Wiley&Sons, Ltd.

 

关键词: Polyazaindolizines;Protonation;13C NMR;1H NMR pKvalues

 

数据来源: WILEY

 

摘要:

AbstractThe pKa, values of six sulmazole analogues were measured spectrophotometrically. The major protonation sites for most of these bridgehead nitrogen heterocycles were determined by1H and13C NMR methods. The aryl‐substituted imidazo[1,2‐a]pyrimidine (4), 8‐methoxyimidazo[1,2‐a]pyrazine (6), imidazo[1,2‐b]pyridazine (9) and imidazo[1,2‐b][1,2,4]triazine (11) undergo protonation at the imidazo nitrogen. The imidazo[1,2‐a]pyrazine (5) protonates mainly at N‐7. In some cases differences in basicity properties between these aryl analogues and the bridgehead heterocycles hav

 

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