Optically active compound, antiferroelectric liquid crystal composition containing the same, process for producing the same and process for producing an optically active carboxylic acid

An antiferroelectric liquid crystal composition containing an antiferroelectric liquid crystal compound and at least one optically active compound represented by the following general formula (1):

• ##STR17## wherein R.sup.1 represents an alkyl or alkoxy group having 5 to 14 carbon atoms;
• R.sup.2 represents an alkyl group having 2 to 12 carbon atoms;
• 1 and m each represents 0 or 1;
• D represents --OCO--,--CH.sub.2 --O-- or --OCOC*R.sup.3 H--, with the proviso that when D is --OCO--, R.sup.4 represents a fluorine atom or a trifluoromethyl group and R.sup.5 represents a hydrogen atom or a fluorine atom, when D is --CH.sub.2 --O--, R.sup.4 represents a methyl group or a trifluoromethyl group and R.sup.5 represents a hydrogen atom, when D is --OCOC*R.sup.3 H--, R.sup.3 is a methyl group, R.sup.4 is a fluorine atom or an alkyl group having 1 to 5 carbon atoms, R.sup.5 is a hydrogen atom, and R.sup.2 may form a ring with R.sup.3 ;
• and C* represents an asymmetric carbon atom.

A process for reducing the threshold voltage of an antiferroelectric liquid crystal composition, which comprises incorporating at least one optically active compound represented by the following general formula (1) into an antiferroelectric liquid crystal or composition thereof to reduce the threshold voltage of the resulting composition:

• ##STR18## wherein R.sup.1 represents an alkyl or alkoxy group having 5 to 14 carbon atoms;
• R.sup.2 represents an alkyl group having 2 to 12 carbon atoms;
• 1 and m each represents 0 or 1;
• D represents --OCO--,--CH.sub.2 --O-- or --OCOC*R.sup.3 H--, with the proviso that when D is --OCO--, R.sup.4 represents a fluorine atom or a trifluoromethyl group and R.sup.5 represents a hydrogen atom or a fluorine atom, when D is --CH.sub.2 --O--, R.sup.4 represents a methyl group or a trifluoromethyl group and R.sup.5 represents a hydrogen atom, when D is --OCOC*R.sup.3 H--, R.sup.3 is a methyl group, R.sup.4 is a fluorine atom or an alkyl group having 1 to 5 carbon atoms, R.sup.5 is a hydrogen atom, and R.sup.2 may form a ring with R.sup.3 ;
• and C* represents an asymmetric carbon atom.

A process for producing of an optically active compound represented by the following general formula (1):

• ##STR19## wherein R.sup.1 represents an alkyl or alkoxy group having 5 to 14 carbon atoms;
• R.sub.2 represents an alkyl group having 2 to 12 carbon atoms;
• 1 and m each represents 0 or 1;
• D represents --OCO--,--CH.sub.2 --O-- or --OCOC*R.sup.3 H--, with the proviso that when D is --OCO--, R.sup.4 represents a fluorine atom or a trifluoromethyl group and R.sup.5 represents a hydrogen atom or a fluorine atom, when D is --CH.sub.2 --O--, R.sup.4 represents a methyl group or a trifluoromethyl group and R.sup.5 represents a hydrogen atom, when D is --OCOC*R.sup.3 H--, R.sup.3 is a methyl group, R.sup.4 is a fluorine atom or an alkyl group having 1 to 5 carbon atoms, R.sup.5 is a hydrogen atom, and R.sup.2 may form a ring with R.sup.3 ;
• and C* represents an asymmetric carbon atom, which comprises reacting a compound represented by the following general formula (2):
• ##STR20## wherein R.sup.1 represents an alkyl or alkoxy group having 5 to 14 carbon atoms;
• 1 and m each represents 0 or 1;
• and W represents hydroxy group, chloromethyl group or bromomethyl group,
• with the following compound represented by general formula (3):
• ##STR21## wherein R.sup.2 represents an alkyl group having 2 to 12 carbon atoms;
• X represents COOH, COCl, a hydroxymethyl group, --C*R.sup.3 HCOOH or --C*R.sup.3 HCOCl with the proviso that when X is COOH or COCl, R.sup.4 represents a fluorine atom or a trifluoromethyl group and R.sup.5 represents a hydrogen atom or a fluorine atom, when X is a hydroxymethyl group, R.sup.4 represents a methyl group or a trifluoromethyl group and R.sup.5 represents a hydrogen atom, when X is --C*R.sup.3 HCOOH or --C*R.sup.3 HCOCl, R.sup.3 is a methyl group, R.sup.4 is a fluorine atom or an alkyl group of 1 to 5 carbon atoms, R.sup.5 is a hydrogen atom, and R.sup.2 may form a ring with R.sup.3 ;
• and C* represents an asymmetric carbon atom.