The photochemical reaction between 1,4-naphthalenedicarbonitrile (NDN) and toluene in acetonitrile is extended to bibenzyl (4), 3- and 4-fluorotoluene (8, 7), and 3- and 4-m ethoxytoluene (9, 10). The product distribution obtained with com pounds 4, 7 and 10 is similar and includes 4-benzyl-1-naphthalencarbonitriles (1a -c), 1-benzyl-1,2-dihydro-1,4-naphthalenedicarbonitriles (5a-c), cis 2-benzyl-1,2-dihydro-1,4-naphthalenedicarbonitriles (2a-c) (with com pound 10 also the trans isomer 12),

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... ubstituted 6,11-dicyano-5,11-methano-5,6,11, 12-tetrahydrodibenzo[ a,e]cyclooctenes (3a, b) (not obtained with com pound 10), besides the hydrocarbons arising from the coupling o f the respective benzyl radicals (products 6a-c). With com pound 9 the only process observed is reduction of NDN to 1,2-dihydronaphthalene-1,4-dicarbonitrile (11). The results obtained fit into the previously proposed mechanistic scheme, involving electron and proton transfer follow ed either by in cage radical coupling to form products 2, 3, 5 and 12 or radical escape leading to products 1 and 6. The effect of substituents on the various phases of the reaction is discussed.