Hydration and hemiacetal formation in oxo-[m . n]metacyclophanes

[m . 2]Metacyclophanes with an oxo-function in the C2 bridge exhibit an enhanced carbonyl reactivity towards nucleophiles. The equilibrium constants for hydration and hemiacetal formation markedly decrease asm increases and qualitatively correlate with the ring strain present in the parent hydrocarbon. [m . n]Metacyclophanes withm,n ≥ 3 are almost free from intraanular steric strain. Accordingly, oxo-functions in the bridges do not exhibit an appreciable enhancement of reactivity.