Analysis of the NMRspectra of five heptahelicenes and some related compounds reveals that annelation of heptahelicene by one or more benzo groups results in a conformational change of the helix. The extent and direction of this change was deduced correctly from the NMRspectra by application only of the ring current theory and the influence of Van der Waals forces, as could be established from the
Photodehydrocyclizations in stilbene-like compounds—III
作者:W.H. Laarhoven、T.H.J.H.M. Cuppen、R.J.F. Nivard
DOI:10.1016/s0040-4020(01)93139-4
日期:1970.1
Photodehydrocyclizations in stilbene-like compounds take place only if the sum of the free valence numbers of the atoms concerned in the cyclization step exceeds in the excited state, a value of 1. If more than one cyclization is possible the photoconversion follows the pathway for which ΣF* is maximal; if ΔΣF* for various cyclizations is smaller than 0·1 a second product is sometimes formed.
Bucky-bowls. A general approach to benzocorannulenes: synthesis of mono-, di- and tri-benzocorannulenes
作者:Goverdhan Mehta、P. V. V. Srirama Sarma
DOI:10.1039/a908852k
日期:——
We outline a conceptually simple and general route to
bowl-shaped benzocorannulenes based on readily assembled PAHs which on
flash vacuum pyrolysis result in the sequential formation of a five- and
six-membered ring; following this approach, syntheses of mono-, di- and
tri-benzocorannulenes have been achieved.