Process for the preparation of thioxanthones

A process for the preparation of at least one thioxanthone represented by Formula I:

• which process comprises adding a reactant mixture of a 2-chlorothiobenzoyl chloride represented by Formula II:
• and an aromatic compound represented by Formula III:
• to a slurry of a Friedel-Crafts catalyst in an organic Friedel-Crafts solvent, wherein:
• R1 and R2 are each independently selected from hydrogen, halogen, C1-10-alkyl, C6-12-aryl or C1-10-alkoxy radicals,
• R3, R4 and R5 are each independently selected from hydrogen, halogen, hydroxyl, C1-10-alkyl, C5-8-cycloalkyl, C6-12-aryl, C1-10-alkoxy, —X1—C(O)OR6, —C(O)R7, —C(O)OR8 or —C(O)NR9R10, or R3 and R4 together form a fused ring having from 5 to 7 ring members,
• X1 is C1-10-alkylene,
• R6, R7 and R8 are independently selected from C1-10-alkyl, C6-12-aryl or C7-11-aralkyl, and
• R9 and R10 are independently selected from hydrogen, C1-10-alkyl, C6-12-aryl or C7-11-aralkyl.