Regioselectivity and mechanism of dihalocarbene addition to benzocyclopropene.
Dihalocarbenes add regioselectively to aryl-substituted benzocyclopropenes to produce dihalobenzocyclobutenes. The regioselectivity of addition is not due to steric effects but depends on the electronic donor or acceptor ability of the substituent. B3LYP/6-31G* calculations show preferential :CCl2 addition to substituted benzocyclopropene through electrophilic attack on the benzocyclopropene pi-system (Ea = 1.1-2.4 kcal/mol) rather than C-C sigma-bond insertion into the cyclopropenyl moiety (Ea = 5-24 kcal/mol). pi-Addition proceeds regioselectively through a single transition state to xylylene intermediates or directly to benzocyclobutene products.
Khrapunovich
Marina
M
Department of Chemistry, Barnard College, 3009 Broadway, New York, New York 10027, USA.
Zelenova
Ekaterina
E
Seu
Lillian
L
Sabo
Alexis N
AN
Flaherty
Aidan
A
Merrer
Dina C
DC