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.
作者:Steven M. Allin、William R.S. Barton、W. Russell Bowman、Emma Bridge (née Mann)、Mark R.J. Elsegood、Tom McInally、Vickie McKee
DOI:10.1016/j.tet.2008.06.014
日期:2008.8
Alkyl radicals have been cyclised onto pyrroles, imidazoles and pyrazoles, and acyl radicals cyclised onto pyrroles, using Bu3SnH-, (TMS)3SiH- and Bu3GeH-mediated aromatic homolytic substitution for the synthesis of bicyclic N-heterocycles. The reactions yield intermediate π-radicals that lose hydrogen in the rearomatisation step of the aromatic homolytic substitution. Mechanistic studies of these
Synthesis by Radical Cyclization and Cytotoxicity of Highly Potent Bioreductive Alicyclic Ring Fused [1,2-a]Benzimidazolequinones
作者:Mary Lynch、Sarah Hehir、Paul Kavanagh、Dónal Leech、John O'Shaughnessy、Michael P. Carty、Fawaz Aldabbagh
DOI:10.1002/chem.200601450
日期:2007.4.5
values for the cytotoxicity of benzimidazolequinones towards the human skin fibroblast cell line GM00637 were in the nanomolar range, as determined by using the MTT assay. The benzimidazolequinones were much more cytotoxic than indolequinone analogues. 1,2,3,4-Tetrahydropyrido[1,2-a]benzimidazole-6,9-dione was the most potent compound prepared being more than 300 times more cytotoxic than the clinically
Radical cyclisation onto pyrazoles: synthesis of withasomnine
作者:Steven M. Allin、William R.S. Barton、W.Russell Bowman、Tom McInally
DOI:10.1016/s0040-4039(02)00763-3
日期:2002.6
A novel synthetic protocol for the synthesis of [1,2-b]-fused bicyclic pyrazoles has been developed using radicalcyclisation. The protocol uses cyclisation of pyrazole-1-(ω-alkyl) radicals generated from 1-[ω-(phenylselenyl)alkyl]-pyrazole precursors. The pyrazole natural product, withasomnine (3-phenyl-5,6-dihydro-4H-pyrrolo[1,2-b]pyrazole), and larger ring analogues have been synthesised in good
使用自由基环化已经开发了用于合成[1,2- b ]-稠合的双环吡唑的新颖合成方案。该协议使用了由1- [ω-(苯基硒基)烷基]-吡唑前体生成的吡唑-1-(ω-烷基)自由基的环化作用。使用该方案可以高收率合成吡唑天然产物withasomnine(3-phenyl-5,6-dihydro-4 H -pyrrolo [1,2- b ] pyrazole)和较大的环类似物。用作中间π自由基氧化剂的偶氮或Et 3 B自由基引发剂可促进Bu 3 SnH介导的氧化环化机理。