Oxidative radical cyclisations onto imidazoles and pyrroles using Bu3SnH
摘要:
Oxidative radical cyclisation using Bu3SnH has been used for the synthesis of [1,2-c]-fused imidazoles and [1,2-a]-fused pyrroles from imidazolecarbaldehydes and acylpyrroles respectively. The intermediate nucleophilic N-alkyl radicals cyclise onto imidazole and pyrrole rings followed by oxidative re-aromatisation. (C) 1997 Elsevier Science Ltd.
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
A new protocol using radical cyclisation has been developed for the synthesis of [1,2-c]-fused imidazoles and [1,2-a]-fused pyrroles. The intermediate nucleophilic N-alkyl radicals, generated using Bu3SnH from N-(omega-bromoalkyl) or N-[omega-(phenylselanyl)alkyl] imidazoles and pyrroles, undergo regioselective radical cyclisation onto the azole rings followed by oxidative re-aromatisation, (C) 1999 Elsevier Science Ltd. Ail rights reserved.