The present invention relates to a process for providing a compound of formula (IV): wherein R1 and R2 are each independently C1-C4 alkyl, and Hal is independently Cl or Br, the process comprising the steps of: (i) reacting a compound of formula (II) wherein R1 and Hal is defined as above, to obtain a compound of formula (III) wherein R1 and Hal is defined as above, and (ii) reacting the compound of formula (III) to obtain the compound of formula (IV).