开发了一种使用二硫代氨基甲酸根阴离子作为催化剂的基于S N 2 的光化学策略,用于活化苄基卤化物,这在作为可见光光催化中的自由基前体应用时极具挑战性。通过这种无过渡金属和无氧化剂的方案,各种杂环的苄基化(或氰基甲基化)包括喹喔啉-2(1 H )-酮、香豆素、2-苯基-2 H-吲唑、1-甲基-5-苯基吡嗪-2(1 H )-one、1-(氟甲基)cinnolin-4(1 H )-one 和 2,4-dibenzyl-1,2,4-triazine-3,5(2 H ,4 H ) -二酮可以实现(46 个例子,高达 98% 的产率)。重要的是,一些生物学相关的 3-benzylquinoxalin-2(1 H)-也可以在温和条件下合成。
BI-OAc-Accelerated C3–H Alkylation of Quinoxalin-2(1<i>H</i>)-ones under Visible-Light Irradiation
作者:Xiang-Kui He、Juan Lu、Ai-Jun Zhang、Qing-Qing Zhang、Guo-Yong Xu、Jun Xuan
DOI:10.1021/acs.orglett.0c02080
日期:2020.8.7
photoredox-catalyst-free radical alkylation of quinoxalin-2(1H)-ones has been described. This reaction utilizes 4-alkyl-1,4-dihydropyridines (R-DHPs) as alkyl radicalprecursors and acetoxybenziodoxole (BI-OAc) as an electron acceptor to undergo single-electron transfer with photoexcited R-DHPs. The benign conditions allow for good compatibility in the scope of both quinoxalin-2(1H)-ones and R-DHPs. The
benzylsulfonyl hydrazides as benzylating agents has been demonstrated in the directC-3benzylation of quinoxalin-2(1H)-ones. A range of benzylsulfonyl hydrazides participated in the C-3benzylation of quinoxalin-2(1H)-ones with CuCN as the catalyst and DTBP as the oxidant, delivering structurally diverse 3-benzylquinoxalin-2(1H)-ones in moderate to good yields.