Novel Catalysis of Hydroquinone Autoxidation with Nitrogen Oxides
摘要:
An efficient catalytic method is described for the preparative conversion of hydroquinones to quinones with dioxygen under mild conditions. The use of the gaseous nitrogen oxide (NOx) catalyst allows a simple workup procedure for the isolation of quinones in essentially quantitative yields by merely removing the low-boiling solvent dichloromethane in vacuo. The mechanism of the catalytic autoxidation of hydroquinones is ascribed to the critical role of nitrosonium (NO+) in the one-electron oxidation of hydroquinone, followed by the reoxidation of the reduced nitric oxide (NO) with dioxygen. An extensive series of complex interchanges among various NOx species in nitrogen-(V), -(IV), -(III), and -(II) oxidation states, coupled with stepwise oxidation of hydroquinone via a successive series of one-electron/proton transfers, form the critical components of the catalytic cycle.
In the presence of a catalytic amount of iodine, hexamethyldisilane can reductively silylate p-quinones under mild conditions to afford 1,4-bis(trimethylsiloxy)arenes in high yields.
Highly Efficient and Chemoselective Reductive Bis-silylation of Quinones by Silyltellurides
作者:Shigeru Yamago、Hiroshi Miyazoe、Kazunori Iida、Jun-ichi Yoshida
DOI:10.1021/ol006581e
日期:2000.11.1
[GRAPHICS]Silyltellurides serve as new silicon-based chemoselective reducing agents and reduce quinones to the corresponding bis-silylated hydroquinones. The reaction proceeds under ambient thermal conditions without the need of any additional promoters or catalysts and gives the products in excellent yields. Several control experiments suggest that the reaction is initiated by a single electron transfer from silyltellurides to quinones.