|Budget Amount *help
¥2,600,000 (Direct Cost : ¥2,600,000)
Fiscal Year 1998 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1997 : ¥1,800,000 (Direct Cost : ¥1,800,000)
Raney nickel is commonly used for the reduction of the carbon-sulfur bonds of sulfides, sulfoxides, and sulfones to the carbon-hydrogen bonds, Secondary alcohols are, however, known to suffer from epimerization with Raney nickel. This epimerization (or racemization) becomes a major drawback in the development of asymmetric synthesis using the sulfur atom. Engaged in finding a solution to the above problem, we could accomplish our purpose of the chemnical research.
1.During our research for the novel tandem Michael addition - MPV reduction to reduce alpha, beta-unsaturated ketones to optically active secondary alcohol using chiral 1,3-mercaptoalcohol (published in J.Am. Chem. Soc.), we found that the Raney nickel (W-2) - sodium hypophosphite combination system worked well for the problem mentioned above.
2.We have found that the Raney nickel - sodium hypophosphite - aceate buffer combination system was an excellent reagent for reductive desulfurization of optically active sulfide-containi
ng alcohols to give secondary alcohols in high yields without any loss of the optical purity (published in Tetrahedron Lett.).
3.We disclosed the scope and limitations : the new reductive desulfurization : sulfoxides as well as sulfides bearing an optically active alcohol gave the corresponding secondary alcohols in high yields without any loss of the optical purity, but sulfones were remained intact (published in Tetrahedromi as a full paper)
4.In addition to the reductive desulfurization, this combination system showed (1) a unique desulfurization of benzylthio or phenylthio ethers in the presence of benzyl ether, (2) the reductive desulfurization of dithioacetals or monothioacetals, (3) the selective 1,2- or 1,4-reduction of alpha, beta-unsaturated ketones depending on the substrates (will be published elsewhere).
These features of the Raney nickel - sodium hypophosphite combination system would be extremely useful in organic syntheses, especially asymmetric synthesis using chiral organosulfur reagents. Less