Compounds with bridgehead nitrogen 52—NMR spectra and stereochemistry of the 2-alkylperhydroimidazolo[3,4-a]pyridines
作者:Lee Banting、Trevor A. Crabb
DOI:10.1002/mrc.1260250808
日期:1987.8
perhydro‐oxazolo[3,4‐a]pyridine and perhydrothiazolo[3,4‐a]pyridine, which adopt equilibria in CDCl3 solution at room temperature containing ca 70% trans‐fused conformers in equilibria with O‐ or S‐inside cis‐fused conformers, 2‐alkylperhydroimidazolo[3,4‐a]pyridines are found to adopt equilibria containing >98% trans‐fused conformers. Comparison of NMR parameters of 2‐methylperhydroimidazolo[3,4‐a]pyridine with those
与全氢恶唑并[3,4-a]吡啶和全氢噻唑并[3,4-a]吡啶相反,它们在室温下在CDCl3溶液中采用平衡,其中含有约70%的与O-或S-平衡的互变构象异构体在顺式融合的构象异构体中,发现 2-烷基全氢咪唑并[3,4-a]吡啶采用含有>98% 的反式融合构象异构体的平衡。2-甲基全氢咪唑并[3,4-a]吡啶的NMR参数与1,2-二甲基全氢咪唑并[3,4-a]吡啶的两种异构体的NMR参数的比较表明前一种化合物在两种反式融合构象异构体之间达到平衡,大约 83% 的构象包含氮孤对电子的反式排列。这些观察结果是根据广义异头效应来解释的。