Compounds of the formula (I) 1 in which: R1 is H, F, CF3, OCF3, OCF2H, OCFH2, an alkyl radical or an alkenyl radical; R2 is H, an alkyl radical or alkyloxy radical or an alkenyl or alkenyloxy radical; G2nullG1 is nullCHnullCHnull, nullCH2CH2null, nullCFnullCHnull, nullCHnullCFnull, nullCFnullCFnull, nullCH2null, nullCF2null; M1, M2 are each, independently of one another, nullC(nullO)Onull, nullOC(nullO)null, nullCH2Onull, nullOCH2null, nullOCF2null, nullCF2Onull, nullCnullCnull, nullCH2CH2null, nullCF2CF2null or a single bond; A1, A2 are each, independently of one another, phenylene-1,4-diyl, unsubstituted, monosubstituted or disubstituted by F, cyclohexane-1,4-diyl, 1,3-dioxan-2,5-diyl; m, n are each, independently of one another, zero or 1; mnullnnull0 or 1; The invention furthermore provides a liquid-crystal mixture comprising one or more compounds of the formula (I) in an amount of 1 to 40% by weight, based on the liquid-crystal mixture and liquid-crystal displays containing this liquid-crystal mixture.