T. Yamato et al., MEDIUM-SIZED CYCLOPHANES .35. SYNTHESIS AND ELECTROPHILIC AROMATIC-SUBSTITUTION OF 8,14,22,28-TETRASUBSTITUTED [2.0.2.0]METACYCLOPHANES, Journal of chemical research. Synopses, (5), 1995, pp. 168-169
Friedel-Crafts acetylation of anti-8,14,22,28-tetramethyl[2.0.2.0]meta
cyclophane (anti-13a) occurs selectively at the 5,11,19,25-positions t
o afford the tetraacetyl derivative anti-18a in 67% yield, whereas in
other electrophilic substitutions this selectivity is not observed.