CORRELATION OF STRUCTURE AND TRANS-ANNULAR INTERACTIONS IN A SERIES OF CAGE COMPOUNDS

A series of cage systems with general structure 7 were synthesized. By variation of bridge C, the distance between functional groups A and B could be changed systematically and the chemical consequences of these changes investigated. Thus, Diels-Alder reactions between benzoquinone and cyclic dienes ranging from cyclobutadiene to cycloheptadiene, and including cyclooctatetraene, yielded endo dienes which were subsequently converted to cage structures photochemically. This transformation results in compounds 8, 10, 15, 16, and 17 with two transannular carbonyl groups positioned at varying distances. Under ketalization conditions some of these compounds-the ones with larger bridges C which brought the keto g oups closer together-gave cyclized products rather than simple ketals. In the other cases, monoketals formed which were reduced to endo alcohols and studied further. Molecular mechanics calculations on hydrocarbon models for these systems provided a more quantitative basis for interpretation of the experimental results. The distance between A and B in 7 varied with the size of bridge C. The calculated energies of simulated ring-closure reactions (40→ 39 and 41 →39) became more favorable as the number of atoms in bridge C was increased. These results parallel the experimental trends. © 1979, American Chemical Society. All rights reserved.