|Budget Amount *help
¥14,800,000 (Direct Cost: ¥14,800,000)
Fiscal Year 2003: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2002: ¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 2001: ¥11,000,000 (Direct Cost: ¥11,000,000)
Nucleophilic addition reactions to the carbaldehyde or imino groups at the 2-position of 1-sullinylnaplithalene have been examined. The reactions examined are as follows : Grignard reactions, alkylation reactions with alkyllithiums, reductions with LiAlH_4 or diisobutylaluminum hydride and Mukaiyama aldol reactions. Stereoselectivity was found dependent on the substituents on the sulfinyl group. High stereoselectivity (>98:2) could be achieved in the reactions of suffinylnaphthaldehyde having a 2,4,6-triisopropylphenyl group. On the other hand, tert-butylsulfinyl-naphthaldehyde or -naphthylmethanimine showed lower stereoselectivities which, however, were in good accord to the ratio of the diastereomers caused by the rotational barrier around the carbon-sulfur bond axis evidenced by the nmr analyses. We have concluded that the high stereoselectivity in the reactions of 1-(2,4,6-triisopropylphenyl)sulfinyl-2-naphthaldehyde or -naphthylmethanimine is caused by the high rotational barrier
around the carbon-sulfur bond axis, because all the reactions shown above proceeded with high stereoselectivities irrespective of the chelating or non-chelating transition states. Furthermore, 1-p-tolylsulfinyl-benzaldehyde or -phenylmethanimine, in which a free rotation around the carbon-sulfur bond axis is assumed, showed high stereoselectivity only in the reaction through chelating transition states. The sulfinyl group can be removed from the products. For example, optically active alcohols especially having two aromatic groups can be prepared very efficiently. Thus, the present reaction provides a new efficient preparative method for optically active methanol having two different aromatic groups, with a similar bulkiness such as phenyl-p-tolylmethanol which is mostly difficult to prepare by the asymmetric reduction.
Reduction of β-ketosuklfoxides with Dibal was found to show complete stereoselectivity which was controlled by the silyl group at the β-position. In this study a new chiral ligand having a rotational barrier for enantioselective reactions was also successfully designed. Thus, a ferrocenyl compound having sulfinyl and diphenylphosfinyl groups at 1-and 1'-positions was found to be an afficient chiral ligand for the allylation of malonate with a Pd catalyst.
Through these studies, we could develop new stereoselective reactions caused by rotational barriers which includes a new concept of stereoselective reactions using a rotational barrier around the carbon-sulfur bond axis. Less