Compound of the formula I in which W denotes -O- or -S-, Y 1 and Y 2, independently of one another, denote H, F, CI, CN or CF 3, R 11 and R 12, independently of one another, denote H, an alkyl or alkenyl radical having up to 15 C atoms which is unsubstituted, monosubstituted by CN or CF 3 or at least monosubstituted by halogen, where, in addition, one or more CH 2 groups in these radicals may be replaced by -O-, -S-, -C=C-, -CF 2 O-, -OCF 2 -, -OC-O- or -O-CO- in such a way that O atoms are not linked directly to one another, R 2 denotes an alkyl or alkenyl radical having up to 15 C atoms which is unsubstituted, monosubstituted by CN or CF 3 or at least monosubstituted by halogen, where, in addition, one or more CH 2 groups in these radicals may be replaced by -O-, -S-, -C=C-, -CF 2 O-, -OCF 2 -, -OC-O- or -O-CO- in such a way that O atoms are not linked directly to one another, furthermore H, halogen, CN, SCN or SF 5, A 1 denotes a 1,3-cyclopentylene radical, which may be monounsaturated and which may be mono- or polysubstituted by a group L, B 1 on each occurrence, identically or differently, denotes, a) a 1,4-phenylene radical, in which one or two CH groups may be replaced by N, b) a 1,4-cyclohexenylene or 1,4-cyclohexylene radical, in which one or two non-adjacent CH 2 groups may be replaced by -O- or -S-, or a cyclobutane-1,3-diyl radical, c) a radical from the group 1,4-bicyclo[2.2.2]-octylene, spiro[3.3]heptane-2,6-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydro-naphthalene-2,6-diyl, thiophene-2,5-diyl, where the groups a), b) and c) may be mono- or polysubstituted by a group L, L on each occurrence, independently, denotes F, CI, CN, SCN, SF 5 or straight-chain or branched, in each case optionally fluorinated alkyl, alkoxy, alkylcarbonyl, alkoxy-carbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, Z 1 and Z 2 in each case, independently of one another, denote a single bond, -CF 2 O-, -OCF 2 -, -CF 2 S-, -SCF 2 -, -CH 2 CH 2 -, -CF 2 CF 2 -, -CF 2 CH 2 -, -CH 2 CF 2 -, -CHF-CHF-, -C O-, -OC -, -CH 2 O-, -OCH 2 -, -CH 2 S-, -SCH 2 -, -CF=CH-, -CH=CF-, -CF=CF-, -CH=CH- or -C≡C-, n denotes 0. W denotes -O- or -S-, Y 1 and Y 2, independently of one another, denote H, F, CI, CN or CF 3, R 11 and R 12, independently of one another, denote H, an alkyl or alkenyl radical having up to 15 C atoms which is unsubstituted, monosubstituted by CN or CF 3 or at least monosubstituted by halogen, where, in addition, one or more CH 2 groups in these radicals may be replaced by -O-, -S-, -C=C-, -CF 2 O-, -OCF 2 -, -OC-O- or -O-CO- in such a way that O atoms are not linked directly to one another, R 2 denotes an alkyl or alkenyl radical having up to 15 C atoms which is unsubstituted, monosubstituted by CN or CF 3 or at least monosubstituted by halogen, where, in addition, one or more CH 2 groups in these radicals may be replaced by -O-, -S-, -C=C-, -CF 2 O-, -OCF 2 -, -OC-O- or -O-CO- in such a way that O atoms are not linked directly to one another, furthermore H, halogen, CN, SCN or SF 5, A 1 denotes a 1,3-cyclopentylene radical, which may be monounsaturated and which may be mono- or polysubstituted by a group L, B 1 on each occurrence, identically or differently, denotes, a) a 1,4-phenylene radical, in which one or two CH groups may be replaced by N, b) a 1,4-cyclohexenylene or 1,4-cyclohexylene radical, in which one or two non-adjacent CH 2 groups may be replaced by -O- or -S-, or a cyclobutane-1,3-diyl radical, c) a radical from the group 1,4-bicyclo[2.2.2]-octylene, spiro[3.3]heptane-2,6-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydro-naphthalene-2,6-diyl, thiophene-2,5-diyl, where the groups a), b) and c) may be mono- or polysubstituted by a group L, a) a 1,4-phenylene radical, in which one or two CH groups may be replaced by N, b) a 1,4-cyclohexenylene or 1,4-cyclohexylene radical, in which one or two non-adjacent CH 2 groups may be replaced by -O- or -S-, or a cyclobutane-1,3-diyl radical, c) a radical from the group 1,4-bicyclo[2.2.2]-octylene, spiro[3.3]heptane-2,6-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydro-naphthalene-2,6-diyl, thiophene-2,5-diyl, where the groups a), b) and c) may be mono- or polysubstituted by a group L, L on each occurrence, independently, denotes F, CI, CN, SCN, SF 5 or straight-chain or branched, in each case optionally fluorinated alkyl, alkoxy, alkylcarbonyl, alkoxy-carbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, Z 1 and Z 2 in each case, independently of one another, denote a single bond, -CF 2 O-, -OCF 2 -, -CF 2 S-, -SCF 2 -, -CH 2 CH 2 -, -CF 2 CF 2 -, -CF 2 CH 2 -, -CH 2 CF 2 -, -CHF-CHF-, -C O-, -OC -, -CH 2 O-, -OCH 2 -, -CH 2 S-, -SCH 2 -, -CF=CH-, -CH=CF-, -CF=CF-, -CH=CH- or -C≡C-, n denotes 0.