In the laser-jet (LJ) photolysis (λ exc 333, 351, and 364 nm, high intensity) of 1-[(4-benzoylphenoxy)methyl]naphthalene (1), a two-photon process is observed in CCl 4 to yield 1-(chloromethyl)naphthalene (3a) as the main product, while the one-photon products of the conventional photolysis (low intensity) are 1,2-di(1-naphthyl)ethane (2), 1,1,1-trichloro-2-(1-naphthyl)ethane (3b), and 1-naphthaldehyde (5). In MeOH or EtOH, however, our results suggest even a three-photon reaction in which 1-naphthylmethyl methyl ether (4c) and 1-naphthylmethyl ethyl ether (4b) are produced in addition to the one-photon product 2. The three-photon mechanism is based on a competition experiment in which ether 1 was irradiated in mixtures of CCl 4 and methanol. The ratio of the two high-intensity products ether 4c and 1-(chloromethyl)naphthalene (3a) showed a strong intensity dependence. We propose that the electronically excited 1-naphthylmethyl radical 1-NpCH 2 • * is photochemically ionized to 1-naphthylmethyl cation 1-NpCH 2 + under the high-intensity LJ photolysis conditions and the latter trapped by the respective alcohols to give the 1-naphthylmethyl ethers 4c and 4b. With the help of time-resolved laser flash photolysis (248 nm) of 1-[(4benzoylphenoxy)methyl]naphthalene (1), it was established that homolysis of the C-O bond to yield 1-naphthylmethyl (1-NpCH 2 • ) and 4-benzoylphenoxy (ArO • ) radicals takes place. The authentic 1-NpCH 2 • and ArO • radicals were generated independently by pulse radiolysis of 1-(bromomethyl)-or 1-(chloromethyl)naphthalene in 2-propanol and of 4-hydroxybenzophenone (6) in water (1% tBuOH); in the latter case, SO 4 •-was used as oxidant. In the LJ photolysis, the triplet state of the 1-naphthylmethyl moiety is probably further excited to yield the observed products.

In the high-intensity laser-jet (LJ) photolysis of 9-(phenoxymethyl)anthracene (1a) and 9,10-bis(phenoxymethyl)anthracene (1b) multiple-photon chemistry was observed. Thus, while the [4 + 4] photodimer 8a was formed as the one-photon product in the low-intensity conventional photolysis of monoether 1a, the high-intensity irradiation in the laser-jet yielded 1,2-bis(9-anthracenyl)ethane (3a), lepidopterene (4a), biplanene (5a), 9-(chloromethyl)anthracene (6a), and 9-(methoxymethyl)anthracene (7a) as main products. The product distribution depended on the solvent used:  after C−O homolysis of the ether 1a, for which at least two photons are required, the resulting arylmethyl radical 2a dimerizes in benzene, in methylene chloride it engages in photoinduced electron transfer, while in methanol it undergoes photoionization. With the help of time-resolved laser-flash photolysis of the monoether 1a it was confirmed that the homolysis of the C−O bond leads to the 9-anthracenylmethyl radical 2a. The authentic radical 2a was generated independently by time-resolved pulse radiolysis and laser-flash photolysis of 9-(bromomethyl)anthracene. Analogous to the monoether 1a, the bisether 1b gave under the high intensity conditions of the laser-jet irradiation tetrabenzo[2.2]paracyclophane (3b), its photodimer (5b), 9,10-(bischloromethyl)anthracene (6b), and 9-(chloromethyl)-10-(phenoxymethyl)anthracene (9b); their distribution depended also on the solvent used. Mechanistic pathways are offered for these multiple-photon processes.

In laser-jet (LJ) photolysis (high intensity) of the ether 4-(4-benzoylphenoxymethyl)biphenyl 1 a twophoton process is observed in CCl 4 to yield 4-(chloromethyl)biphenyl 5 as product (3%), while the onephoton product is 4-biphenylaldehyde 7 (100% in conventional photolysis versus 97% in laser-jet photolysis). In ethanol, the results suggest a three-proton reaction in which 4-(ethoxymethyl)biphenyl 6 is produced in appreciable amounts (18%) in addition to the one-photon product 1,2-bis(4-biphenyl)ethane 4, the latter as the major product (82%). It is proposed that under high-intensity LJ photolysis conditions the electronically-excited 4-biphenylmethyl radical 2* is photoionized to the 4-biphenylmethyl cation 2 + and that the latter is trapped by ethanol to give the 4-biphenylmethyl ether 6.