由于甲硅烷基团容易迁移,甲硅烷基甲脒1与其碳烯形式1'处于平衡状态。1与各种取代的氟苯的反应随着亲核卡宾1'的插入而进行在混合试剂后进入最酸性的 C-H 键,不需要任何催化剂。根据 DFT 计算,通过三元过渡态结构进行的插入反应的经典解释需要高活化能。相反,预计将芳香底物中酸性最强的质子转移到卡宾碳上的活化势垒较低。下一步,形成的离子对向产物的无障碍重排完成了该过程。取代苯在与甲硅烷基甲脒反应中的反应性可以通过计算的C-H 氢的p K a (DMSO) 值粗略评估。具有 p K a的苯衍生物约 少于 31 个可以进行 C-H 插入。该反应提供缩醛胺作为第一批产物,它可以很容易地通过酸水解转化为相应的醛。由于甲硅烷基甲脒1对许多官能团具有耐受性,该反应可应用于多种苯衍生物,使其成为有机合成应用的可靠策略。
3-Hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors. 3. 7-(3,5-Disubstituted-[1,1'-biphenyl]-2-yl)-3,5-dihydroxy-6-heptenoic acids and their lactone derivatives
摘要:
The syntheses of a series of 7-(3,5-disubstituted [1,1'-bephenyl]-2-yl)-3,5-dihydroxy-6-heptenoic acids and their lactones are reported. Intrinsic 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitory activity is enhanced markedly when the biphenyl moiety is substituted by chloro or methyl groups at positions 3 and 5 and a fluoro group at position 4'. These substitutions, followed by resolution, provided compounds 100(+) and 110(+) with 2.8 times the intrinsic inhibitory activity of compactin. Compound 100(+) was shown to possess the same chirality in the lactone ring as compactin by single-crystal X-ray crystallography.