Microwave-assisted regioselective olefinations of cyclic mono- and di-ketones with a stabilized phosphorus ylide
作者:Jinlong Wu、Dan Li、Huafeng Wu、Lijie Sun、Wei-Min Dai
DOI:10.1016/j.tet.2005.12.060
日期:2006.5
4-cyclohexanediones with the ylide at 190 °C for 20 min in MeCN afforded the exocyclicolefins in >94:6 isomer ratios. On the other hand, the same reactions carried out at 230 °C for 20 min in the presence of 20 mol % DBU furnished the endocyclicolefins in >83:17 isomer ratios. The base-mediated isomerization of the exocyclicolefins into the endocyclic isomers was primarily driven by thermodynamic stability of the
Highly regioselective Wittig reactions of cyclic ketones with a stabilized phosphorus ylide under controlled microwave heating
作者:Jinlong Wu、Huafeng Wu、Shaoyong Wei、Wei-Min Dai
DOI:10.1016/j.tetlet.2004.03.198
日期:2004.5
Significant base and temperature effects on the Wittig reactions of cyclohexanones with (carbethoxymethylene)triphenylphosphorane under microwave irradiation were observed. For the Wittig reactions carried out in a domestic microwave oven under solvent-free conditions, the initially formed exo-olefin products isomerized into the thermodynamically more stable endo-olefins due to uncontrolled high reaction temperature. In sharp contrast, under controlled microwave heating, both exo- and endo-olefins have been selectively synthesized by accurately regulating the reaction temperature with or without a base. (C) 2004 Elsevier Ltd. All rights reserved.
Harding; Haworth; Perkin, Journal of the Chemical Society, 1908, vol. 93, p. 1968
作者:Harding、Haworth、Perkin
DOI:——
日期:——
Perkin; Pope; Wallach, Journal of the Chemical Society, 1909, vol. 95, p. 1795,1798