Bispyridylnorbornadienes were synthesized using the Diels–Alder reaction of HBF4 salts of bispyridylacetylenes with cyclopentadiene. They underwent the photocyclization to give quadricyclanes which reverted to norbornadienes by heating or a catalyst. Bis(N-methylpyridyl)norbornadienes were also synthesized and the photoreactions were investigated.
prepared using the Diels–Alder reaction of the HBF4 salts of dipyridylacetylenes with cyclopentadiene. Their absorptions extend to 380 nm and are red-shifted in an acidic media. They underwent photocyclization to give quadricyclanes which reverted to norbornadienes upon heating or encountering a Co(II)–TPP catalyst. 2,3-Bis(1-methylpyridinio)norbornadienes were also prepared by a Diels–Alder reaction of