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These photocatalyzed radical conjugate addition reactions are carried out in a meso-scale flow photoreactor consisting in coils of UV-transparent FEP tubing wrapped around a water-cooled medium pressure mercury vapor lamp.

The photochemical behavior of methyl-substituted aromatic γ,δ-epoxy ketones was investigated by irradiation with a 500 W high-pressure mercury lamp in benzene which led to the formation of 4-methyleneisochromanols through δ-hydrogen abstraction–epoxy rearrangement–1,5-biradical cyclization reactions.

The title catalysts are prepared from suspensions of TiO2 nanoflakes in EtOH solutions of AgNO3 (3 h in the dark), followed by illumination with a 300 W high pressure mercury lamp for 3 h, and calcination at 500 °C for 3 h and 8 h in air.

Benzofuroxan 5, upon irradiation using a high pressure mercury lamp with a Pyrex filter in acetonitrile containing a little water, afforded 1H-azepine-2,7-dione 6. The initial stage of this reaction would be formation of a highly reactive intermediate possessing two nitrile oxide functions. On the other hand, when compound 5 was irradiated using a low pressure mercury lamp in acetonitrile containing a little water, it afforded 6H-furazano[4,5-c]carbazole 3-oxide 11 and compound 6. The structure of compound 11 was determined by an X-ray structural analysis. In the presence of an aromatic hydrocarbon, the formation of compound 11 was decreased and that of compound 6 was increased. Mechanistic studies on the photoreaction suggest that the photosensitized formation of compound 6 with the aromatic hydrocarbon may be carried out by the reabsorption of the fluorescence of it near 365 nm and the presence of it may quench the formation of compound 11.

The large shifts (−30.5 and +41.7 cm−1, respectively) of the IR absorption lines of nitric acid (HONO2) in a N2 matrix in the ν1 (OH stretching) and ν3 (HON bending) vibrational modes, relative to those observed for HONO2 in an Ar matrix, indicate a strong interaction between HONO2 and N2. Photolysis of HONO2 in solid Ar produced predominantly HOONO, whereas relatively intense lines of N2O and HONO were observed after photolysis of HONO2 in solid N2 with a mercury lamp, with the relative yield of HOONO decreased by more than a factor of 10. Possible photochemical processes are discussed.

Irradiation of 8-azatricyclo[3.2.1.02,4]oct-6-enes in dry ether with a low pressure mercury lamp gave azabishomobenzenes through [2π+2σ]-type migration reactions between C–N bonds and olefin moieties.

4,8-Dialkylbenzo[1,2-d;4,5-d′]bis[1,2,3]trithioles 2 were readily oxidized by m-chloroperbenzoic acid, N-bromosuccinimide and N-iodosuccinimide to form both benzobistrithiole 1 - and 2-oxides (4 and 5), and the ratio was dramatically affected by the kind of oxidizing agent used. Irradiation of the oxidized produts, benzobistrithiole 2-oxides 5, in acetonitrile with a high-pressure mercury lamp gave benzobistrithiole 1 -oxides 4 quantitatively. Photolysis of benzo- and naphtho-trithiole 2-oxides also yielded benzo- and naphtho-trithiole 1 -oxides. These photochemical oxygen migrations were shown to proceed intramolecularly via an excited singlet state by 18O-labelled, cross-over and triplet quencher experiments.

When pyrido[2,3-c]furoxan 4 was irradiated in acetonitrile containing a little water with a low pressure mercury lamp, 3-nitro-2-pyridone 5 was obtained. When compound 4 was irradiated in the presence of morpholine with a low pressure mercury lamp in an argon atmosphere, 6-morpholinopyridine 2,3-dioxime 6, 6-morpholinopyrido[2,3-c]furazan 7, 3-amino-6-morpholino-2-nitropyridine 8, and 3-amino-4,6-dimorpholino-2-nitropyridine 9 was produced. The results of photoreaction study indicated the only photo-product to be compound 6. The main difference between these two reactions may be considered due to the behavior of nitrogen in the pyridine ring.

Photolysis of 2-fluoro-2′,5′-dimethyldiphenylamine 1a, in ethanol with a medium-pressure mercury lamp, gave a mixture of 1,4-dimethylcarbazole 7 (53%), 8-fluoro-1,4-dimethylcarbazole 2(11%) and 6-ethoxy-2-fluoro-2′,5′-dimethyldiphenylamine 8(19%). Photolysis of 4-fluoro-2′,5′-dimethyldiphenylamine 1b gave 6-fluoro-1,4-dimethylcarbazole 25 (35%) and 1,4-dimethylcarbazole 7(47%).

N-Benzoyl-N-benzylcinnamamides 1, N-acetyl-N-(1-benzyl)cinnamamides 3 and N-[(1-benzyl)aminocarbonyl]-N-(1-benzyl)cinnamamides 5 have been irradiated by a high-pressure mercury lamp in the presence of benzil in benzene at room temperature to give 3-azatricyclo[5.2.2.01,5]undeca-8,10-dien-4-ones 2, 4 and 6 with high stereoselectivity. These are the first photo[4+2]cycloadducts of an enone and a benzene ring.

Azulenequinones gave dimers when they were irradiated with a high-pressure mercury lamp. In polar solvents, head-to-head dimers were predominant, whereas head-to-tail dimers increased in less polar solvents. From 3-methoxy-1,5-azulenequinone, four products were obtained, while bromoazulenequinones and 1,5-azulenequinone gave a single dimer. The product distribution was dependent on the polarity of solvents, substituents, and concentrations.

A novel self-coupling reaction in alcohol or hexane-water of cycloalkanone (cycloheptanone, cyclooctanone, and cyclododecanone) with irradiation under a high-pressure mercury lamp yielded the corresponding pinacol-type compound in good yields. In the case of cyclohexanone, 2-methyl-, 2-phenyl-, 4-methylcyclohexanone, 5α- and 5β-cholestan-3-one, the pinacol derivatives were not obtained and the dimethyl acetals were given.

Heating of o-allyl-substituted acylbenzenes with potassium tert-butoxide in DMF with simultaneous irradiation from a high-pressure mercury lamp afforded substituted naphthalenes, including arylnaphthalenes. 2-(o-Tolyl)-substituted aromatic aldehydes were converted into phenanthrenes under the same conditions. A formal synthesis of tanshinone I has also been achieved.

One-way EZ-isomerization of bis(n-butylammonium) (Z,Z)-muconate [(Z,Z)-hexa-2,4-diene-1,6-dioate] to the corresponding (E,E)-isomer quantitatively proceeded in the crystalline state under photoirradiation with a high-pressure mercury lamp, being a new type of crystal-to-crystal reaction.

Photo-oxygenation of 4,5,6,8,12,13,14,16-octamethyl[2.2]metacyclophane using a high-pressure mercury lamp produced a mixture of mono- and bis-endoperoxides in quantitative yield, while irradiation with sunlight in chloroform afforded 1,2,3,6,7,8-hexamethyl-trans-10b, 10c-dimethyl-10b,10c-dihydropyrene in 20% yield.

A series of 4,5-bis-(alkyn-1-yl)imidazoles—‘imidazole-fused’ enediynes—were synthesized and their reactivities in photoinduced Bergman cycloaromatization reactions were determined. The more conformationally rigid analogues gave cycloaromatized products in good yields upon irradiation (450 W low-pressure mercury lamp, ambient temperature). A bicyclic analogue ( 3 ) was shown to cleave supercoiled plasmid DNA.

The synthesis of substituted anthracenes from naphthalene precursors is described. The key step involved heating ortho -allyl substituted naphthalene-2-carbaldehydes and potassium t -butoxide in DMF with concomitant irradiation from a high pressure mercury lamp to afford anthracenes in yields of 76–98%.

The photoirradiation of thionophosphates, ROP(S)(OEt)2, derived from benzyl and vinylogously benzyl alcohols in CH3CN, with a Hanovia medium-pressure mercury lamp in a quartz vessel leads to the formation of the corresponding thiolophosphates, RSP(O)(OEt)2, through a non-chain radical pathway. This behavior of thionophosphates is unlike that of the related phosphates, which react through ionic dissociation–recombination processes. When the irradiation is conducted in solvents such as PriOH, THF and toluene, benzylation of these solvents takes place in synthetically respectable yields. Irradiation of thionophosphates in CH3CN leads to a convenient allylic benzylation of olefins.

Treatment of 2-(o-tolyl)- or 2-(3-methyl-2-pyridyl)-substituted indole-3-carbaldehydes with potassium tert-butoxide in DMF at 70–80 °C with simultaneous irradiation from a 400 W high-pressure mercury lamp afforded benzo[a]carbazoles and pyrido[2,3-a]carbazoles respectively in good yields.

Ion-exchangeable layered titano-niobates, CsNbTi2O7 and CsNbTiO5, were prepared and the photocatalytic properties of those oxides as well as of the H+-exchanged forms were investigated. H2 or O2 evolution reaction from an aqueous methanol solution or from an aqueous silver nitrate solution was carried out under a high pressure mercury lamp irradiation. For H2 evolution, Pt (0.1 wt%)-loaded H+-exchanged forms showed remarkable activity both for CsNbTi2O7 and CsNbTiO5, while higher rates of O2 evolution were obtained for H+-exchanged forms than those for the original forms.

An acetonitrile solution of acetylene and 3-methylcyclopent-2-enone (4) was irradiated with Pyrex-filtered light from a mercury lamp to give 5-methylbicyclo[3.2.0]hept-6-en-2-one (6) and 6-methyltricyclo[4.1.0.02,7]heptan-3-one (8). These were easily separated and when heated under reflux in ButOH with SeO2 gave the 4-methyltropone valence-tautomer 5-methylbicyclo[3.2.0]hept-3,6-dien-2-one (10) and 4-methyltropone (12), respectively, the latter in 20% overall, unoptimized yield. Similar reactions with 3-isopropylcyclopent-2-enone (5) in the place of (4) led to the natural troponoid 4-isopropyltropone (nezukone)(13).

Two photochemical methods for the preparation of arenetricarbonylchromium(0) complexes are described. The first involves irradiation of a solution of hexacarbonylchromium(0) and arene in THF at room temperature with a medium pressure mercury lamp. In the second a suspension of hexacarbonylchromium(0) in THF is irradiated in the same way and the arene then added. The yields are generally lower than those obtained by the usual thermal methods, but there is advantage in the milder reactions conditions.

The photoaddition of acrylonitrile to mesityl oxide was accomplished at 355 nm with high quantum yield (15%) using a pulsed laser (intensity= 9 MW/cm 2 , pulse duration 13 ns, repetition rate= 10Hz) and selectively led to three products in contrast to irradiation with a mercury lamp which principally gave an acrylonitrile polymer and with continuous wave laser (intensity= 5.7 W/cm 2 ) which gave a much lower quantum yield (0.4%).