Diels-Alder cycloadditions using nucleophilic 3-(p-tolylthio)-2-pyrone. Regiocontrolled and stereocontrolled synthesis of unsaturated, bridged, bicyclic lactones
作者:Gary H. Posner、Todd D. Nelson、Chris M. Kinter、Neil Johnson
DOI:10.1021/jo00041a009
日期:1992.7
Captodative 3-(tolylthio)-2-pyrone (1) is shown to be reactive as a nucleophilic diene undergoing 2 + 4-cycloadditions with various electrophilic alkenes under sufficiently mild thermal conditions (less-than-or-equal-to 90-degrees-C) so that the initial bicyclic lactone adducts can be isolated on gram scale in moderate to very good yields (42-82%) without loss of CO2. These bicyclic adducts are formed regiospecifically and often with excellent stereoselectivity. These Diels-Alder cycloadditions are the first examples of a captodative unsaturated sulfide acting as an enophile. NMR data (C-13) are presented correlating the electron density in the pyrone diene systems with their Diels-Alder reactivity, and some transformations of the bicyclic lactone adducts are shown to illustrate the value and versatility of these richly functionalized synthetic intermediates.
3-Cuprio-2-pyrone: an extraordinary organocopper reagent
作者:Gary H. Posner、Wayne Harrison、David G. Wettlaufer
DOI:10.1021/jo00225a008
日期:1985.12
POSNER, G. H.;HARRISON, W.;WETTLAUFER, D. G., J. ORG. CHEM., 1985, 50, N 25, 5041-5044
作者:POSNER, G. H.、HARRISON, W.、WETTLAUFER, D. G.
DOI:——
日期:——
POSNER, G. H.;HARRISON, W., J. ORGANOMET. CHEM., 1985, 285, N 1-3, C27-C30
作者:POSNER, G. H.、HARRISON, W.
DOI:——
日期:——
An organometallic route to (±)3-p-toluenesulfinyl- 2-pyrone
作者:Gary H. Posner、Wayne Harrison
DOI:10.1016/0022-328x(85)87397-6
日期:1985.4
3-Bromo-2-pyrone reacts with dimethylcopperlithium and then with p-tolyl p-toluenethiosulfonate to form 3-p-toluenethio-2-pyrone. Organocopper species are likely intermediates in this reaction. Oxidation of the sulfide produces (±)-3-p-toluenesulfinyl-2-pyrone. The overall process involves an important and useful umpolung, a reversal of reactivity at C(3) of the pyrone ring from an electrophilic center