Benzene derivatives of the formula (I); wherein R1 and R2, are the same or different and independently are selected from the group consisting of hydrogen, alkyl, aralkyl, —CHO, —CH2OR3, —CH(OR4)(OR5) and —COOR6, wherein R3, R4 and R5 are the same or different and are selected from hydrogen, alkyl, aryl, alkaryl, aralkyl, alkylcarbonyl or arylcarbonyl, or wherein R4 and R5 together form an alkylene group and wherein R6 is selected from hydrogen, alkyl and aryl, are prepared in a process, which comprises: reacting a furan derivative of formula (II): wherein R1 and R2 have the meanings above, with ethylene under cycloaddition reaction conditions in the presence of an acid solvent to produce the benzene derivative, wherein the acid solvent is a carboxylic acid and is present in a weight ratio acid solvent to furan derivative from 1:1 to 250:1.