A New Reaction Manifold for the Barton Radical Intermediates: Synthesis of <i>N</i>-Heterocyclic Furanosides and Pyranosides via the Formation of the C<sub>1</sub>−C<sub>2</sub> Bond
作者:Jong Uk Rhee、Brian I. Bliss、T. V. RajanBabu
DOI:10.1021/ja028617z
日期:2003.2.1
The first radical intermediate in the thiourethane-mediated deoxygenation of an alcohol (Barton-McCombie reaction) can participate in an exo-hex-5-enyl- or exo-hept-6-enyl-type radical cyclization when a suitable radical acceptor (e.g., alpha,beta-unsaturated ester, oxime ether, or hydrazone) is appropriately placed. Carbohydrate-derived imidazolyl and triazolyl thiourethanes with such acceptors, upon addition to excess of a good hydride donor (reverse addition), undergo efficient cyclization reactions to give N-heterocyclic furanosides, and, surprisingly even N-pyranosides. Depending on the acceptor, glycosides with either a C(2)()-amino or a C(2)()-carbon substituent are formed.