Efficient catalytic reduction of ketones with formic acid and ruthenium complexes
作者:Naim Menashe、Einat Salant、Youval Shvo
DOI:10.1016/0022-328x(95)05995-2
日期:1996.5
ring-substituted derivatives were found to act as efficient catalysts in reduction reactions of aldehydes and ketones to alcohols, using formic acid as H source. Excess formic acid accelerates the reaction, and the corresponding formate esters were isolated as sole products. Turnover numbers of up to 8000 (alcohols) and 11 000 (formate esters) were attained, with yields in the order of 90%. Alkenes are not reactive
Functionalized tetraarylphthalimides or diarylphthalimides fused with an acenaphthene moiety have been prepared in one step from 2-bromomaleimide and tetraarylcyclopentadienones (tetracyclones) or 7,9-diaryl-8H-cyclopentacenaphthylene-8-ones (acecyclones). The reaction, involving a cycloaddition-decarbonylation-dehydrobromination sequence, gives high isolated yields and is compatible with the presence of various functional groups.
Catalytic disproportionation of aldehydes with ruthenium complexes
作者:Naim Menashe、Youval Shvo
DOI:10.1021/om00057a019
日期:1991.11
It was discovered that the ruthenium complex [(C4Ph4COHOCC4Ph4)(mu-H)][(CO)4Ru2] (2), as well as other isostructural Ru complexes, in the presence of a catalytic amount of formic acid, catalyzes the homogeneous bimolecular disproportionation reaction of aldehydes to give esters: 2RCHO --> RCOOCH2R. The reaction was found to be general and compatible with a variety of aliphatic and aromatic aldehydes and can be carried out in the presence or absence of solvent under mild conditions. It is characterized by an excellent efficiency with an initial turnover frequency reaching 5000 h-1, a measured overall turnover number of ca. 20 000, and high conversion, yield, and selectivity. Increasing the electron density on the metal and the ligand was found to accelerate the reaction. Kinetic studies indicate that the rate = k[catalyst]1/2[aldehyde]. The rate also depends on the initial formic acid concentration. A stoichiometric reaction of complex 2 with formic acid, monitored by infrared spectroscopy, shed light on the identity of the active catalytic species. No kinetic isotope effect could be detected by using PhCDO and DCOOD as reactants. Consequently, a mechanism and a detailed catalytic cycle for the bimolecular transformation of aldehydes to esters were proposed.