ENONES WITH STRAINED DOUBLE-BONDS .3. CYCLOADDUCTS FROM BICYCLO[3.3.1]NON-1-EN-3-ONE

Reaction of the bicyclic bromo ketone 2b with triethylamine yields the bridgehead enone 1 which is rapidly trapped by any nucleophile present in the reaction solution. In the absence of competing nucleophiles, the enone 1 is trapped by a slower reaction with furan to form the Diels-Alder adducts 9 and 10. If the reaction solution contains neither nucleophiles nor furan, the enone 1 undergoes a 2 + 2 cycloaddition reaction with itself to form the symmetrical dimers 14, 15, and 16. These same dimers are produced in approximately the same proportions when the enone 1 is generated by a retro-Diels-Alder reaction of the adducts 9 and 10 in a pyrolysis tube. © 1979, American Chemical Society. All rights reserved.