THE PHOTOCHEMICAL REACTION OF 1,4-NAPHTHALENEDICARBONITRILE WITH AROMATIC PINACOLS AND PINACOL ETHERS

Article abstract of DOI:10.1016/S0040-4020(01)88083-2

Irradiation of 1,4-naphthalenedicarbonitrile (NDN) in deoxygenated acetonitrile in the presence of aromatic pinacols (1) leads to reduction of the former to the dihydro derivative 4 and the tetrahydro derivative 5 as well as to oxidative cleavage of the latter to yield ketones or aldehydes (3).Reaction with pinacol ethers (2) leads to product types 3,4 and 5 as well as to 1(1-methoxybenzyl)-1,2-dihydro NDN derivatives (two diastereoisomers, 6 and 7).Only one of these adducts is formed in the reaction of NDN with benzyl methyl ether (8).The reaction involves electron transfer to singlet excited NDN and cleavage of the radical cations 1^+. and 2^+. to yield α-hydroxy and α-methoxy radicals, respectively.These react with NDN by proton transfer in the first case, and by carbon-carbon bond formation in the latter.The stereoselectivity observed in the adduct formation with 8 is explained by deprotonation of the radical cation and reaction of the corresponding radical with NDN^-. in the geminate solvent cage.The mechanism of these reactions is discussed in the light of a recent flash-photolysis study.