Synthesis of Medium-Sized Bicyclic Compounds by Intramolecular Cyclization of Cyclic<i>β</i>-Keto Radicals Generated from Cyclopropanols Using Manganese(III) Tris(pyridine-2-carboxylate) and Its Application to Total Synthesis of 10-Isothiocyanatoguaia-6-ene
olefinic side chain are oxidized with manganese(III) tris(pyridine-2-carboxylate) to generate cyclic β-keto radicals with ring-expansion. These cyclize intramolecularly, affording bicyclic radical intermediates. The cyclized radicals are trapped with various radical-trapping reagents such as electron-rich or -deficient olefins, tributylstannane and diphenyl diselenide to give the corresponding functionalized
Generation of β-Keto Radicals from Cyclopropanols Catalyzed by AgNO<sub>3</sub>
作者:Shunsuke Chiba、Zhengyan Cao、Serry Atta Atta El Bialy、Koichi Narasaka
DOI:10.1246/cl.2006.18
日期:2006.1
Various β-keto radicals are generated from cyclopropanols by treatment with a catalytic amount of AgNO3 and (NH4)2S2O8 as a reoxidant in the presence of pyridine. Thus, generated β-keto radicals react with alkenes to yield addition products.
Tertiary cyclopropanol compounds react with a catalytic amount of vanadyl acetylacetonate in the presence of oxygen affording beta-hydroxyketones and beta-diketones. For 3-substituted-bicyclo[4. 1.0]alkanols, peroxides are obtained, as are the beta-hydroxyketones. Conversely, 2-ethoxycarbonylcyclopropyl silyl ethers produce ethyl gamma-oxocarboxylate derivatives given the same reaction conditions. (c) 2005 Elsevier Ltd. All rights reserved.