The present invention relates to Use of a compound of the general formula (I), (II), (III), (IV), (V) or (VI) wherein R1 and R1', R21 and R21', R31 and R31' are the same and are hydrogen, a linear or branched C1 to C18 alkyl, a linear or branched C2 to C18 alkenyl, a linear or branched C1 to C10 alkoxy, a linear or branched C1 to C9 alkoxycarbonyl, a linear or branched C1 to C9 alkanoyloxy, aminocarbonyl, hydroxycarbonyl, a linear or branched C1 to C9 alkoxyalkyl, an unsubstituted cycloalkyl, a linear or branched C1 to C6 alkyl substituted cycloalkyl, preferably an unsubstituted cyclohexyl, an unsubstituted C6 to C12 aryl, a linear or branched C1 to C4 alkyl substituted C6 to C12 aryl, or C7 to C12 aralkyl, R2 and R2', R22 and R22', R32 and R32' are the same and are hydrogen, a linear or branched C1 to C18 alkyl, a linear or branched C1 to C9 alkoxyalkyl, or R2 and R2' form together with R1 and R1' respectively, R22 and R22' form together with R21 and R21' respectively, R32 and R32' form together with R1 and R1' respectively, a 5 or 6 membered unsaturated or saturated carbocyclic ring optionally comprising 1 or 2 oxygen atoms, X is selected from the group consisting of hydrogen, fluoro, chloro, bromo, iodo, alkoxycarbonyl, aminocarbonyl, hydroxycarbonyl, a linear or branched C1 to C18 alkyl, a C1 to C18 alkenyl, a linear or branched C2 to C10 alkenyl, a sulfonate and OR50, wherein R50 is selected from the group consisting of hydrogen, a linear or branched C1 to C18 alkyl, and a linear or branched C1 to C9 alkylcarbonyl, and Y is selected from the group consisting of hydrogen, fluoro, chloro, bromo, iodo, a linear or branched C1 to C18 alkyl, a C1 to C18 alkenyl, a linear or branched C2 to C10 alkenyl, a sulfonate and OR50, wherein R50 is selected from the group consisting of hydrogen, a linear or branched C1 to C18 alkyl, and a linear or branched C1 to C9 alkylcarbonyl, R60 is selected from the group consisting of hydrogen, hydroxy and C1 to C18 alkoxy, and R61 is selected from the group consisting of hydrogen, hydroxy, C1 to C10 alkylsulfonyl-C1 to C5, and C1 to C18 alkyl as solvent, in particular as polar solvent, for chemical reactions, for recrystallizations or extractions.