Nitrogen bridgehead compounds. Part 51 Autoxidation of 9-aminotetrahydro-4<i>H</i>-pyrido[1,2-<i>a</i>]pyrimidin-4-ones. Synthesis and stereochemistry of 9-amino- and 9-hydroxy-6,7-dihydro-4<i>H</i>-pyrido[1,2-<i>a</i>]-pyrimidin-4-ones
作者:Tibor Breining、István Hermecz、Benjamin Podányi、John Sessi
DOI:10.1002/jhet.5570220523
日期:1985.9
9-phenylaminotetrahydro-4H-pyrido[1,2-a]pyrimidin-4-ones 1-5 were oxidized into the 9-aminodihydro compounds 15-19 by atmospheric oxygen at ambient temperature. Autoxidation is most probably a free-radical chain process, which takes place with ground-state triplet oxygen via the radical cation of the enamine form. The 9-aminodihydro derivatives were also prepared from 9,9-dibromo compounds 10 and 11 and from 9-hydroxydihydro
在溶液中,在环境温度下,由大气中的氧将9-苯基氨基四氢-4 H-吡啶并[1,2 - a ]嘧啶-4-酮1-5氧化为9-氨基二氢化合物15-19。自氧化反应很可能是自由基链过程,它与基态三线态氧通过烯胺形式的自由基阳离子发生。9-氨基二氢衍生物还由9,9-二溴化合物10和11和9-羟基二氢化合物12-14制备。由9-氨基化合物16、19和21获得的9-羟基二氢衍生物通过酸性水解,显示出溶剂依赖性和R 1取代基依赖性的氧-烯醇互变异构现象。烯醇形式通过吸电子的R 1基团和极性溶剂来稳定。然而,对于9-氨基二氢吡啶并[1,2- a ]嘧啶15-26,仅烯胺互变异构体(E)可以独立于取代基和溶剂而被鉴定。通过紫外,红外,1 H-和13 C-nmr光谱研究了合成产物的化学结构。