Medium-sized cyclophanes. Part 31. Synthesis and electrophilic substitution of 8-substituted metacyclo(1,3)pyrenophanes
syn- and anti-2,11-Dithia metacyclo(1,3) pyrenophanes 15 have been obtained by coupling the corresponding 1,3-bis(bromomethyl)pyrene 11 and 1,3-bis(mercaptomethyl)benzenes 14 in ethanol under high-dilution conditions. Oxidation of the obtained thiametacyclophanes 15 with m-chloroperbenzoic acid afforded the corresponding syn- and anti-disulfones 18. Pyrolysis of the syn- and anti-disulfones 18 afforded exclusively the corresponding anti-metacyclo(1,3)pyrenophane 19 in 40–70% yield along with the ring-cleavage product, 7-tert-butyl-1,3-dimethylpyrene 8. The nitration of 5,15-di-tert-butyl-8-methyl-19b and 5,15-di-tert-butyl-8-methoxy-metacyclo(1,3)pyrenophane 19d with 1 mol equiv. of copper(II) nitrate in acetic anhydride solution exclusively occurred on the more reactive pyrene ring to afford 14-nitro derivatives 21a and 21b in 83 and 86% yield, respectively. On the other hand, the bromination of substrates 19 with bromide in methylene dichloride solution afforded 13-bromo derivatives 23 along with the transannular cyclization products 24 and 25. These different orientations for the electrophilic substitution are also discussed.