Solvent-Controlled, Site-Selective <i>N</i>-Alkylation Reactions of Azolo-Fused Ring Heterocycles at N1-, N2-, and N3-Positions, Including Pyrazolo[3,4-<i>d</i>]pyrimidines, Purines, [1,2,3]Triazolo[4,5]pyridines, and Related Deaza-Compounds
作者:Brett C. Bookser、Michael I. Weinhouse、Aaron C. Burns、Andrew N. Valiere、Lino J. Valdez、Pawel Stanczak、Jim Na、Arnold L. Rheingold、Curtis E. Moore、Brian Dyck
DOI:10.1021/acs.joc.8b00540
日期:2018.6.15
coordinated to sodium indicated a potential role for the latter reinforcing the N2-selectivity. Limits of selectivity were tested with 26 heterocycles which revealed that N7 was a controlling element directing alkylations to favor N2 for pyrazolo- and N3 for imidazo- and triazolo-fused ring heterocycles when conducted in THF. Use of 1H-detected pulsed field gradient-stimulated echo (PFG-STE) NMR defined
使用NaHMDS作为碱,在THF中用碘甲烷将4-甲氧基-1 H-吡唑并[3,4- d ]嘧啶(1b)烷基化,选择性地提供了N2-甲基产物4-甲氧基-2-甲基-2 H-吡唑并[3,相对于N1-甲基产物(2b),以8/1的比例存在4- d ]嘧啶(3b)。有趣的是,在DMSO中进行反应使选择性逆转,以提供4/1的N1 / N2甲基化产物比例。产品3b的晶体结构N1和N7与钠配位表明后者可能增强N2选择性。用26个杂环测试了选择性极限,结果表明,当在THF中进行反应时,N7是控制烷基化的控制元素,对于吡唑并环而言,该环对吡唑并环反应有利于N2,对咪唑和三唑并稠合的环杂环则有利于N3。使用1个H-检测脉冲场梯度受激回波(PFG-STE)NMR确定的离子反应性复合物的分子量。该数据和DFT电荷分布计算表明,紧密离子对(CIP)或紧密离子对(TIP)控制THF中的烷基化选择性,而溶剂分离的离子对(SIPs)是DMSO中的反应性物质。