Synthesis of annularly functionalized cyclophanes

Friedel–Crafts reaction of m- and p-benzenedicarboxylic acid chlorides with toluene gave diketones. The dicarbonyl dibromides, obtained by NBS bromination of diketones were coupled with various dithiols and dihydroxy benzenes to give cyclophanes incorporating two carbonyl groups. The dicarbonyl dibromide, derived from isophthalic acid chloride was converted into dithiol, which on coupling with the same dibromide afforded cyclophane incorporating four carbonyl groups. The NaBH4 reduction of the tetraketone cyclophane in methanol gave the tetraalcohol derivative.