High-Pressure Mercury Lamps

With short periods of irradiation (with high-pressure mercury lamps) under oxygen in chloroform containing methylene blue as a sensitizer, variously substituted 2-arylthiazoles are converted in the corresponding 2-aryloxazoles (823). 

On the other hand, 2-arylthiazoles are easily isomerized to 3-aryliso-thiazoles in 407o yield upon irradiation with a high-pressure mercury lamp, in benzene solution in the presence of iodine (738). A valence bond isomerization was proposed among several alternatives to account for these results. 

The photolysis of 4-substituted 2,3-dimethyl-3-isoxazolin-5-ones has been studied. Irradiation in methanol or ethanol with a 100 W high-pressure mercury lamp through a Pyrex filter of a 4-phenylthio compound produced a semithioacetal (Scheme 5). In contrast, an H, Cl or OPh moiety gave no reaction. The use of alkylthio substitution gave similar products. Cyclic compounds yielded cyclic products (Scheme 5), and the photolysis of (29) in benzene... 

Perhydrodlpyrldlno(l,2-a][l, 2 -c]-pyrlmldlne (2). (a) To an ice-cooled solution of 2-(2-(pipendyl)ethyll pipendine 1 (3.2 g, 10 2 mmol) in EtaO (200 mL) was added N-chlorosuccinimlde (NCS) (1.7 g, 12 7 mmol) Under stirring, the reaction mixture was inadated with a 300 W high pressure mercury lamp under N2 for 5 h. The precipitate was filtered, dryed and extracted with n-pentane Evaporation of the solvent and distillation gave 1.0 g of 2 (50%). bp 140 C (20 torr)... 

Irradiations of Testosterone Acetate (114), —In t-Butanol. 1.25 g of (114) in 250 ml t-butanol is irradiated for 32 hr at 30° under nitrogen with a Hanau Q81 high-pressure mercury lamp placed in a central water-cooled Pyrex immersion well with acetone filter. The solvent is evaporated in vacuo and the residue chromatographed on 125 g silica gel with benzene-ethyl acetate (4 1) to yield 0.29 g 17 -hydroxy-la,5 -cyclo-10a-androstan-2-one acetate [(118) 23%] mp 164-165°, after crystallization from acetone-hexane [a]i3 37 (CHCI3) 0.14 g cyclopentanone (120) (11%) mp 106-107° [aJo 38° (CHCI3) and 0.58 g starting material [(114) 46%]. Ratio (118) (120) - 2 1. 

Sensitized by Acetophenone. A -butanol solution of (114) (2.10 M) and acetophenone (0.8 M) is irradiated for 6 hr at 30° under nitrogen with a Hanau Q 81 high-pressure mercury lamp through a Pyrex-acetone filter (path length 1 cm, cut-off of wavelengths below 3270 A). Better than 98 % of the incident light is absorbed by the acetophenone. A 70% conversion of (114) to the same products as listed above is observed. The ratio (118) (120) is again -2 1. 

A solution of 5 g of (267) in 140 ml of benzene is irradiated for 24 hr at 15-20° with a 70-W Hanau Q81 high pressure mercury lamp in a central pyrex immersion well. A stream of ethylene is bubbled through the solution during the irradiation. After evaporation of the solvent the residue is... 

Irradiation of piperidine 62 in CH2CI2 at concentration of 3mg/ml in the presence of 1-methylimidazole using a high-pressure mercury lamp (150 w) yielded 2-phenyl-4,6,7,8,9,9n-hexahydropyrido[2,l-h][l, 3]oxazin-4-one (01 SI258). 

The proposed mechanism is based on the basis of the fact that ylides (Scheme 23 and Scheme 24) undergo bond fission between the phosphorus atom and the phenyl group in TPPY as reported by Nagao et al. [51] and between the sulfur atom and the phenyl group in POSY as observed in triphenylsulfonium salts [52-55] when they are irradiated by a high-pressure mercury lamp. The phenyl radicals thus produced participate in the initiation of polymerization. 

Previously, the same author [52] reported that compounds containing the tricoordinated sulfur cation, such as the triphenylsulfonium salt, worked as effective initiators in the free radical polymerization of MMA and styrene [52]. Because of the structural similarity of sulfonium salt and ylide, diphenyloxosulfonium bis-(me-thoxycarbonyl) methylide (POSY) (Scheme 28), which contains a tetracoordinated sulfur cation, was used as a photoinitiator by Kondo et al. [63] for the polymerization of MMA and styrene. The photopolymerization was carried out with a high-pressure mercury lamp the orders of reaction with respect to [POSY] and [MMA] were 0.5 and 1.0, respectively, as expected for radical polymerization. 

A mixture of ethyl 3,5-dimethyl-l/f-thieno[2,3-c]-1,2-diazepine-l-carboxylate (6) (10-15%) and the isomeric ethyl 2,5-dimethyl-3//-thieno[2,3-t/]-l, 3-diazepine-3-carboxylate (8) (50-60%) is obtained when a solution of the thienopyridine A-iminc 4 in benzene is irradiated with a 400-W high-pressure mercury lamp for 2-3 hours at 20rC. It has been suggested that product 6 is formed from the intermediate 5. The isomeric intermediate 7 undergoes two consecutive walk rearrangements, followed by valence tautomerization, to give the major product 8.168... 

Irradiation of a benzene solution of 7-benzyl-2,5-diphenyl-3,4,7-triazanorcara-2,4-diene (15) with a high-pressure mercury lamp (Pyrex filter) results in a photochemical walk rearrangement to give 4-benzyl-3,7-diphenyl-477-l, 2,4-triazepine (16) in 53 % yield, accompanied by A-benzyl-3,6-diphenylpyridazin-4-amine (6%), 1-benzyl-2,3-diphenylpyrrole (1%) and... 

B. 2-Phenylthio-5-heptanol. A photochemical reactor consisting of a tubular pyrex flask, a magnetic stirbar, a water-cooled high pressure mercury lamp, and an argon inlet tube (Note 9) is charged with... 

The low solubility of fullerene (Ceo) in common organic solvents such as THE, MeCN and DCM interferes with its functionalization, which is a key step for its synthetic applications. Solid state photochemistry is a powerful strategy for overcoming this difficulty. Thus a 1 1 mixture of Cgo and 9-methylanthra-cene (Equation 4.10, R = Me) exposed to a high-pressure mercury lamp gives the adduct 72 (R = Me) with 68% conversion [51]. No 9-methylanthracene dimers were detected. Anthracene does not react with Ceo under these conditions this has been correlated to its ionization potential which is lower than that of the 9-methyl derivative. This suggests that the Diels-Alder reaction proceeds via photo-induced electron transfer from 9-methylanthracene to the triplet excited state of Ceo-... 

Irradiation of cyclo-S% dissolved in CS2 by a high-pressure mercury lamp at 20 °C produces the homocycles S7, S, S12, S9, Sio, and probably S5 in concentrations decreasing in this order. Irradiation of Se in CS2 gives mainly Ss and S7 while irradiation of S7 generates Ss and S. Similarly, photolysis of S12 in CS2 yields Ss, S7, and Se [51]. For these reasons UV-Vis spectra of compounds containing S-S bonds must be recorded with caution not to trigger decomposition reactions. 

Light sources are often expensive, especially if made of thick-walled quartz as in high-pressure mercury lamps, and delicate, so that equipment costs may be high compared to thermal processes. 

P 32] Pyrene (20 mM), 1,4-dicyanobenzene (40 mM) and sodium cyanide (1 M) were reacted in propylene carbonate and water. A 100 pi solution of pyrene (20 mM), 1.4-dicyanobenzene (40 mM) in propylene carbonate and a 100 pi solution of sodium cyanide (1 M) in water were fed by programmable dual-syringe pumps via fused-silica capillary tubes into a micro-channel chip [29]. Both solutions were fed with equal flow velocity. A 300 W high-pressure mercury lamp was used as light source. After passing an optical filter made of a CUSO4 solution, the whole chip was irradiated after formation of a stable oil/water interface inside. The oil phase was collected at the exit. 

Thomas and co-workers [277] reported that irradiation of (382) with a 450 W high-pressure mercury lamp brought about photocyclisation to a constrained analogue (394). The structure of the product was elucidated through NMR and X-ray diffraction analysis. The compound retained high affinity for the CBi receptor (Xj = 48 nM) and good selectivity over the CB2 receptor (K[ — 3,340 nM). 

After a few minutes irradiation with a high pressure mercury lamp at about 50 C, a rather complete cover of grafted acrylic acid, acrylamide and other vinyl monomers could be obtained. In later experiments a continuous grafting method has been developed where a tape or a fiber bundle after suitable pretreatment is grafted by UV irradiation for a few seconds. Homopolymer formed is removed by washing and grafted polymer analyzed by dye absorption, IR reflection and ESCA spectroscopy. 

Alkene Linkages. Using (250-350)-nm irradiation (30,31) or the unfiltered light from a high-pressure mercury lamp (32), Balandier and Decker have measured quantum yields under nitrogen... 

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