FORCE FIELD-SCF CALCULATIONS ON CYCLOPROPENE INTERMEDIATES IN CARBENE REARRANGEMENTS. COMPARISON WITH EXPERIMENT

Article abstract of DOI:10.1016/S0040-4020(01)96400-2

Heats of formation and geometries of benzocyclopropene, cyclopropa(b)naphthalene, bicyclo(4.1.0)hepta-2,4,7-triene, and benzannelated derivatives have been calculated with a combined force field-SCF progrsm.The bicycloheptatrienes are stabilized relative to the isomeric arylcarbenes by benzannelation, and destabilized by loss of aromaticity and/or increased strain. 1-Naphthylcarbene, 2-naphthylcarbene, 9-phenanthrylcarbene and 9-anthrylcarbene were generated by gas-phase pyrolysis of the corresponding arene aldehyde tosylhydrazone sodium salts, diazomethanes, or 5-aryltetrazoles, and rearranged to cyclobutanaphthalene(21), cyclobutaphenanthrene(33), and cyclobutaanthracene(38), respectively. 10,11-Dihydrodibenzocyclohepten-5-ylidene (15), similarly generated from 5-diazo-10,11-dihydro-5H-dibenzocycloheptene (39), rearranged to 5a,9b-dihydro-5H-benzo<3,4>cyclobut<1,2-a>indene(40), 5H-dibenzocycloheptene(41), and 8,9-dihydro-4H-cyclopentaphenanthrene(40). 40 rearranged thermally to 41.The mechanisms of the rearrangements are discussed.