Competing isomerizations of [12]annulenes: Diels-Alder reaction versus electrocyclization.
Experimentally, tri-trans-[12]annulene and tris(cyclohexeno)[12]annulene exhibit differing reactivities. Whereas the former, after isomerizing to its di-trans isomer, undergoes sequential electrocyclizations, the latter follows a Diels-Alder pathway after initial electrocyclization. B3PW91/6-31+G*//B3LYP/6-31G* calculations indicate that cyclohexenofusion simultaneously hinders the second electrocyclization and facilitates Diels-Alder reaction, primarily by inducing greater puckering in the intermediate eight-membered ring.
Castro
Claire
C
Department of Chemistry, University of San Francisco, 2130 Fulton Street, San Francisco, California 94117-1080, USA. castroc@usfca.edu
Karney
William L
WL
Noey
Elizabeth
E
Vollhardt
K Peter C
KP