Enhanced carbonyl reactivity and conformational effects in peri-dioxocycloalka[de]naphthalenes

Cycloalka[de]naphthalenes with two peri carbonyl groups in ten-, seven-, and nine-membered rings add water or methanol in the presence of acetic acid with relative rates ten > seven- > nine-membered, but hydrations stop at 17, 30, and 90% respectively. Methanol gives with the ten-and nine-membered diketones respectively, a bridged acetal and a bridged hemiacetal. Force field calculations give minimum energy conformations for the diketones that are confirmed by study of their temperature dependent 1H n.m.r. spectra.