Microwave-assisted, regioselective, Petasis olefination of unsymmetrical oxalates. Formation of pyruvate-based enol ethers and enamines
作者:Matthew J. Cook、Declan W. Fleming、Timothy Gallagher
DOI:10.1016/j.tetlet.2004.11.070
日期:2005.1
The Petasis olefination of unsymmetrical oxalates and oxalate monoesters/monoamides (tert-BuO2CC(O)X, where X = OR, NR2) is highly regioselective and provides pyruvate-based enolether and enamine derivatives. The olefination step occurs under conventional thermal conditions, but is dramatically improved––shorter reaction times and higher yields––when promoted by microwave irradiation.
[(<i>N</i>,<i>N</i>-Dimethylamino)carboxymethylene]pentacarbonylchromium(0): The First Fischer Carbene Complex with a Free Carboxyl Group Attached Directly to the Carbene Atom
作者:Dalimil Dvořák、Miroslav Ludwig
DOI:10.1021/om980082o
日期:1998.8.1
free acid (CO)5CrC(NMe2)CO2H (3). Comparison of the pKa values of 3 (9.36) and Me2NCO−CO2H (9.25) in DMF reveals that the (CO)5CrC(NMe2) moiety is a slightly weaker electron acceptor than the Me2NCO group.
通过Me 2 NCO的反应可轻松制备酯卡宾络合物(CO)4 Fe C(NMe 2)CO 2 t-Bu(2a)和(CO)5 Cr C(NMe 2)CO 2 t-Bu(2b)-CO 2 T-BU(1)为Fe(CO)4 2 -或Cr(CO)5 2 -和在THF溶液氯代三甲基硅烷。的反应图2b与CF 3 CO 2 H ^得到游离酸(CO)5的Cr C(NME 2)CO 2高(3)。比较DMF中p K a值为3(9.36)和Me 2 NCO-CO 2 H(9.25)时发现,(CO)5 Cr C(NMe 2)部分是比Me 2 NCO稍弱的电子受体团体。