A general stereoselective approach to previously unknown 1,2,4-triazepane-3-thiones/ones based on reduction or reductive alkylation of readily available 2,4,5,6-tetrahydro-3H-1,2,4-triazepine-3-thiones/ones has been developed. The approach involved the treatment of tetrahydrotriazepines with sodium cyanoborohydride in MeOH at pH 3 or with sodium borohydride and excess of carboxylic acid in THF to give 1-unsubstituted or 1-alkyl-substituted 1,2,4-triazepane-3-thiones/ones, respectively. The latter were also prepared by the reaction of 1-unsubstituted 1,2,4-triazepane-3-thiones/ones with sodium cyanoborohydride and an aldehyde in MeOH in the presence of AcOH. The stereochemistry of the triazepane-3-thiones/ones obtained was established in DMSO solution and in the solid state using NMR spectroscopy and single-crystal X-ray diffraction. These data and DFT B3LYP/6-311++G(d,p) calculations show that the gauche effect plays a significant role in stabilization of preferred conformations of 1-unsubstituted 1,2,4-triazepane-3-thiones/ones.

中文翻译：

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通过7元环状半咔唑酮和硫代半咔唑酮的还原或还原烷基化作用，可以方便地立体选择新型1,2,4-triazepan-3-ones / thiones

基于易于获得的2,4,5,6-四氢-3 H的还原或还原烷基化反应，对以前未知的1,2,4-三氮杂环庚烷-3-硫酮/酮进行立体选择的通用方法已经开发了-1，2，4-三氮杂-3-硫酮/酮。该方法涉及在pH 3的MeOH中用氰基硼氢化钠的MeOH溶液处理四氢三氮杂卓，或在THF中用硼氢化钠和过量的羧酸处理四氢三氮杂苯，得到1-未取代或1-烷基取代的1,2,4-三氮杂庚烷-3-硫酮/酮， 分别。后者也可以通过使未取代的1,2,4-三氮杂环庚烷-3-硫酮/酮与氰基硼氢化钠和醛在MeOH中，在MeOH中的条件下反应制得。使用NMR光谱学和单晶X射线衍射，在DMSO溶液中和固态下建立了三氮杂环庚烷-3-硫酮/酮的立体化学。这些数据和DFT B3LYP / 6-311 ++ G（d，p）的计算表明，笨拙 在稳定1-未取代的1,2,4-三氮杂环庚烷-3-硫酮/酮的优选构象中起重要作用。