Radical cyclisation onto imidazoles and benzimidazoles
摘要:
New synthetic methodology has been developed for the synthesis of [1,2-a]Fused imidazoles and benzimidazoles using intramolecular homolytic aromatic substitution. In the intramolecular substitution, N-(omega-alkyl) radicals are generated using Bu3SnH from N-(omega-phenylselanyl)aIkyl side chains. Phenylselanyl groups are used as radical leaving groups to avoid problems in the N-alkylation of imidazoles and benzimidazoles. Arylsulfones for imidazoles, and phenylsulfides for benzimidazoles, are used as the leaving groups in the homolytic substitutions. (C) 1999 Elsevier Science Ltd. All rights reserved.
Structurally diverse annulated benzimidazoles were synthesized via two copper(I)-catalyzed cyclocondensation reactions. In the first case the title compounds were prepared from lactams and o-bromoaniline. An alternative route consisted of an intramolecular cyclization of o-bromoarylamidines.
Barton esters for initiator-free radical cyclisation with heteroaromatic substitution
作者:Robert Coyle、Karen Fahey、Fawaz Aldabbagh
DOI:10.1039/c3ob27313j
日期:——
first examples of efficientradicalcyclisation with (hetero)aromatic substitution via Barton ester intermediates. Cyclopropyl and alkyl radicals allow access to five, six and seven-membered alicyclic-ring fused heterocycles with and without an additional fused cyclopropane, including the skeleton of the anti-cancer agent, cyclopropamitosene, expanded, and diazole analogues. Radical initiators are not
There is provided a compound of the formula (I′):
wherein x is a nitrogen or CRx, Rx is a hydrogen, etc., R
1
is an optionally substituted hydrocarbon group, etc., R
2
is an optionally substituted hydrocarbon group, etc., ring A is 5- to 8-membered heterocyclic ring, etc., and each of Y
1
, Y
2
and Y
3
is an optionally substituted carbon or a nitrogen, etc.; or a salt thereof or a prodrug thereof, which have CRF receptor antagonistic activity and use thereof.
Metal-Free Sequential C(sp<sup>2</sup>)–H/OH and C(sp<sup>3</sup>)–H Aminations of Nitrosoarenes and <i>N</i>-Heterocycles to Ring-Fused Imidazoles
作者:Anisha Purkait、Subhra Kanti Roy、Hemant Kumar Srivastava、Chandan K. Jana
DOI:10.1021/acs.orglett.7b00832
日期:2017.5.19
Hydrogen bond assisted ortho-selective C(sp2)–Hamination of nitrosoarenes and subsequent α-C(sp3)-H functionalization of aliphatic amines is achieved under metal-free conditions. The annulation of nitrosoarenes and 2-hydroxy-C-nitroso compounds with N-heterocycles provides a facile excess to a wide range of biologically relevant ring-fused benzimidazoles and structurally novel polycyclic imidazoles
氢键辅助的亚硝基芳烃的邻位选择性C(sp 2)-H氨基化和随后的α-C(sp 3)-H脂肪族胺的官能化在无金属条件下实现。亚硝基芳烃和2-羟基-C-亚硝基化合物与N-杂环的环化分别提供了相对于广泛的生物学相关的环稠合的苯并咪唑和结构上新颖的多环咪唑的简便过量。发现在卤代亚硝基芳烃的C(sp 2)–H胺化过程中,亲核芳香族氢取代(S N ArH)比经典S N Ar反应更可取。
Synthesis of benzimidazoles via iridium-catalyzed acceptorless dehydrogenative coupling
作者:Xiang Sun、Xiao-Hui Lv、Lin-Miao Ye、Yu Hu、Yan-Yan Chen、Xue-Jing Zhang、Ming Yan
DOI:10.1039/c5ob00904a
日期:——
Benzimidazoles were prepared in good yieldsviathe iridium-catalyzed acceptorless dehydrogenative coupling of tertiary amines and arylamines.