78926-56-4Relevant articles and documents
Photochemistry of 3-methyl- and 4-methyl-1,2-dihydronaphthalene in solution
Duguid, Robert J.,Morrison, Harry
, p. 1265 - 1271 (2007/10/02)
Photolysis of 3-methyl-1,2-dihydronaphthalene (3-MDHN) in hexane solution with 254-nm light produces one major product, 5-methylbenzobicyclo[3.1.0]hex-2-ene(5-MBBH; φ = 4.7 × 10-4). Photolysis in hexane in the presence of trifluoroacetic acid produces exclusively 2-methylene-1,2,3,4-tetrahydronaphthalene (2-MTHN). The 254-nm photolysis of 4-methyl-1,2-dihydronaphthalene (4-MDHN) in hexane produces 2-(o-tolyl)-1,3-butadiene (T13B; φ= 2.2 × 10-3), 1-methylbenzobicyclo[3.1.0]hex-2-ene (1-MBBH; φ= 1.4 × 10-3), 1 -methyl- 1,4-dihydronaphthalene (1-M-1,4-DHN; φ= 8.7 × 10-3), 1-methyltetralin (1-MT; φ= 1.5 × 10-3), and 1-methylnaphthalene (1-MN; φ= 2.7 × 10-3). Triplet sensitization of 4-MDHN produces only 1-MN in small amounts, suggesting that the direct photolyses proceed via singlet chemistry. The products appear to derive from a combination of electrocyclic opening of the cyclohexadienyl ring to generate an o-quinodimethane intermediate, disproportionation leading to net oxidation-reduction and, in 4-MDHN, a [1,3] hydrogen shift to form 1-M-1,4-DHN. The o-quinodimethane intermediates further react to form benzobicyclo[3.1.0]hex-2-ene derivatives (via a photochemical [4 + 2] cycloaddition; Scheme VI) and, in the case of 4-MDHN, the 1,3-butadiene T13B (via a thermal [1,5] hydrogen shift; Scheme VII).
