Highly Regio- and Diastereoselective Chromium(0)-Catalysed Cyclopropanation of 1-Alkoxy-1,3-dienes with Diazo Compounds
作者:Norbert D. Hahn、Martin Nieger、Karl Heinz Dötz
DOI:10.1002/ejoc.200300687
日期:2004.3
Pentacarbonyl(η2-cis-cyclooctene)chromium(0) (1) is an efficient catalyst for diazo decomposition and selective [2+1]-cycloaddition reactions of the resulting carbene intermediates with electron-rich dienes. The cyclopropanation of 1-alkoxy-1,3-butadienes 4−8 with 9-diazo-9H-fluorene (2) yields vinylspirocyclopropanes 9−13 in good to excellent yields, as single regioisomers arising from carbene transfer
Photooxygenation of chiral dienol ethers: asymmetric synthesis of alkoxydioxines
作者:Patrick H. Dussault、Qiang Han、Darby G. Sloss、David J. Symonsbergen
DOI:10.1016/s0040-4020(99)00666-3
日期:1999.9
chiral dienolethers provides a new route to alkoxydioxines (alkoxyendoperoxides). Depending upon substitution and geometry, the [4+2] cycloaddition is accompanied or even supplanted by [2+2] cycloaddition leading to alkene cleavage and/or ene-like reaction leading to allylic hydroperoxides. The diastereoselectivity of cycloaddition is ultimately limited by the conformational freedom of the dienol ether
向手性二烯醇醚中添加1 O 2为制备烷氧基二恶英(烷氧基内过氧化物)提供了一条新途径。取决于取代和几何形状,[4 + 2]环加成伴随或什至被[2 + 2]环加成所取代,导致烯烃裂解和/或类似烯的反应导致烯丙基氢过氧化物。最终,二烯醇醚底物的构象自由度限制了环加成的非对映选择性。