title: An Experimental and Computational Investigation of (α-Methylbenzylidene)carbene.
abstract: Photolysis of 1-(1-phenylethylidene)-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene, in C6H6 (or C6D6), at ambient temperature, produces (α-methylbenzylidene)carbene which undergoes a facile Fritsch-Buttenberg-Wiechell (FBW)-type rearrangement to 1-phenylpropyne. The alkyne results exclusively from a 1,2-phenyl shift as evident from the use of a (13)C-labeled precursor. This experimental result is consistent with CCSD(T)/cc-pVTZ//B3LYP/6-31+G* calculations which reveal that a 1,2-phenyl shift in the singlet carbene needs to overcome a barrier of only 3.8 kcal/mol whereas the 1,2-methyl shift has to surmount a much larger barrier of 11.9 kcal/mol. The alkyne remains the predominant product when the photolysis is carried out in cyclohexene but the carbene-alkene cycloadduct could be detected, albeit in low yield, in the photolysate.
authors.affiliation: Department of Chemistry, Colby College , Waterville, Maine 04901, United States.
authors.forename: Xi
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Chemistry, Colby College , Waterville, Maine 04901, United States.
authors.forename: Keith
authors.initials: K
authors.lastname: Languet
authors.affiliation: Department of Chemistry, Colby College , Waterville, Maine 04901, United States.
authors.forename: Dasan M
authors.initials: DM
authors.lastname: Thamattoor