THE DEBROMINATION ROUTE TO NORBORNADIENOMALEIMIDES AND 7-OXANORBORNADIENOMALEIMIDES - STUDY OF CYCLOADDITION SPECIFICITIES WITH CYCLIC DIENES

The debromination route (Zn/Ag in THF) which successfully produces 7-o xanorbornadienes fails in the norbornadiene series owing to different stereochemical positioning of the bromine substituents in the bicyclic precursors. A new oxygen, oxygen repulsive interaction is proposed to play a dominant but not exclusive role in determining stereochemical outcomes in the cycloaddition of 7-oxanorbornadienomaleimides with cyc lopentadiene, furan and 2,5-dimethylfuran. The major product observed experimentally is in complete accord with that predicted by semi-empir ical molecular orbital calculations (AM1).