The optically active alcohol derivative represented by the above formula (III), i.e. an azole type .alpha.,.beta.-unsaturated alcohol derivative is known to be useful as an active ingredient for fungicides, plant growth regulators or herbicides, as represented for example by 1-(2,4-dichlorophenyl)-2-(1,2,4-triazol-1-yl)-4,4-dimethyl-1-penten-3-ol, 1-(4-chlorophenyl)-2-(1,2,4-triazol-1-yl)-4,4-dimethyl-1-penten-3-ol and 1-cyclohexyl-2-cyclohexyl-2-(1,2,4-triazol- 1-yl)-4,4-dimethyl-1-penten-3-ol. And, it is also well known that there is a remarkable difference in the activity between the optical isomers, and that, for example with the foregoing 1-(2,4-dichlorophenyl)-2-(1,2,4-triazol-1-yl)-4,4-dimethyl-1-penten-3-ol and 1-(4-chlorophenyl)-2-(1,2,4-triazol-1-yl)-4,4-dimethyl-1-penten-3-ol, the (-)-isomer has a strong activity as fungicides, while the (+)-isomer has a strong activity as plant growth regulators and herbicides [Japanese Patent Application Kokai (Laid-open) Nos. 99575/1982 and 106669/1982].
For this reason, there is a great demand for the development of a method to produce either one of the (-)- or (+)-optical isomer according to intended uses and yet with a good efficiency in industry.
As the conventionally well-known common reducing agent for reducing the carbonyl group of ketone compounds into alcohol compounds, there are various reagents represented by lithium aluminum hydride and sodium borohydride. The reduction product produced when these reagents are used is an optically inactive, i.e. racemic compound, and when these reagents are used for the reduction of ketone compounds having an unsaturated bond, particularly .alpha.,.beta.-conjugated unsaturated ketones like the material used in the method of the present invention, reduction of the double bond in addition to the carbonyl group is easy to occur, and besides there also comes out a possibility that the steric configuration correlated with the double bond is isomerized.
As the conventionally known asymmetric reduction method for the ketone compound represented by the above formula (I), there is a method in which for example a ketone compound represented by the formula (IV), ##STR7## wherein X represents a hydrogen or chlorine atom, is reduced with an asymmetrically modified lithium aluminum hydride compound to obtain an optically active alcohol compound represented by the formula (V), ##STR8## wherein X and a mark * have the same meanings as above, [Japanese Patent Application Kokai (Laid-open) Nos. 99575/1982 and 106669/1982].
Said method, however, may not always be said to be satisfactory in industry in the following points: (1) Since lithium aluminum hydride is used, there is a danger such as ignition by contact with moisture, and (2) in order to obtain an alcohol compound having a higher optical purity, additives such as N-substituted aniline are required in large amounts.
Also, in asymmetric reduction, the following methods are reported as a method for producing optically active alcohols using an asymmetrically modified boron hydride-reducing agent:
.circle.1 A method of using sodium borohydride and the onium salt of optically active ephedrine [described in S. Colona, et al., J. Chem. Soc., Perkin Trans I, 371 (1978)],
.circle.2 a method of using an optically active amine-borane complex [described in R. F. Borch, et al., J. Org. Chem. 37, 2347 (1972)],
.circle.3 a method of using an a-amino acid ester-borane complex [described in M. F. Grundon, et al., Tetrahedron Letters, 295 (1976)], and
.circle.4 a method of the asymmetric reduction of aromatic ketones with an optically active amino alcohol and borane [described in A. Hirao, et al., J. Chem. Soc. Chem. Comm., 315 (1981); S. Itsuno, et al., ibid. 469 (1983); and S. Itsuno, et al., J. Chem. Soc. Perkin Trans I, 1673 (1983)].
But, the methods .circle.1 , .circle.2 and .circle.3 are too low in optical yield to say that they are a practical method. Also, the method .circle.4 may not always be said to be satisfactory to carry it out in industry because, in order to attain high optical purity, borane of two times by mole, as converted to boron basis, as much as amino alcohol is required.