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
作者:W. Russell Bowman、Peter T. Stephenson、Nicholas K. Terrett、Adrian R. Young
DOI:10.1016/0040-4020(95)00412-2
日期:1995.7
Radical cyclisation of sp3 carbon-centred radicals onto imines and hydrazones provides a new method for the synthesis of 5- and 6-membered ring nitrogen heterocycles. Cyclisation onto the electrophilic carbon of the C=N group and 5-exo stereoelectronic selectivity are the dominating mechanistic parameters. The C-centred radical intermediates were generated from benzeneselenyl precursors using Bu3SnH
Carbocyclic ring expansion reactions via radical chain processes. Part II.
作者:Jack E. Baldwin、Robert M. Adlington、Jeremy Robertson
DOI:10.1016/s0040-4020(01)82331-0
日期:1991.8
The further exploitation of the homolytic ringexpansionreaction of cyclohexanone derivatives is described. The application of this methodology to the preparation of exomethylene cycloalkanones, α-alkylated cyclodecanones, indanones, and decalinols is described.
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
Aromatic homolytic substitution using solid phase synthesis
作者:Steven M. Allin、W. Russell Bowman、Rehana Karim、Shahzad S. Rahman
DOI:10.1016/j.tet.2006.02.071
日期:2006.5
Solid phase synthesis has been used to carry out intramolecular aromatichomolyticsubstitution with benzoimidazole precursors. The protocol attaches the radical precursors to the resins via the radical leaving groups (in the aromatichomolyticsubstitution). When the radical reactions are complete, the leaving group, unaltered starting material and reduced uncylised products remain attached to the