Rayonet reactor

Preparative Photolysis. The preparative photolysis of an aqueous solution (pH=8.5) of AETSAPPE (2.5 M) was conducted in a 1-inch diameter quartz test tube in a Rayonet Reactor (Southern New England Radiation Co.) fitted with 254 nm lamps. Within two hours the solution gelled and the reaction was terminated. Upon acidification the solution cleared, and the product could be re-precipitated by addition of base. This indicates loss of the thiosulfate functionality. The product was dissolved in dilute HC1, precipitated with acetone, and filtered. This process was repeated three times, and the final precipitate was washed with water. The product (20 to 30 mg) was dried in vacuo for 24 hours and stored in a dessicator until use. Comparison of the13 C NMR spectrum of the product with the starting AETSAPPE 13C NMR spectrum clearly shows that the thiosulfate methylene peak shifted upfield, from 39 ppm to 35 ppm. The complete 13 C NMR and IR analysis of the product were consistent with the disulfide product. Further, elemental analysis of the product confirmed that the product was the desired disulfide product 2-amino (2-hydroxy 3-(phenyl ether) propyl) ethyl disulfide (AHPEPED) Expected C 58.39, H 7.08, N 6.20, S 14.18 actual C 58.26, H 7.22, N 6.06, S 14.28. 

Preparative photolysis of AETSAPPE (0.25 M aqueous solution) at 254 nm (Rayonet reactor) resulted in the formation of the disulfide product 2-amino(2-hydroxy-3-(phenyl ether) propyl) ether disulfide (AHPEPED) as the primary photoproduct Photolysis of AETSAPPE at 254 nm (isolated line of medium pressure mercury lamp) resulted in rapid initial loss of starting material accompanied by formation (analyzed by HPLC) of AHPEPED (Figure 12a and 12b) (Scheme IV). Similar results were obtained for photolysis- at 280 nm. Quantum yields for disappearance of AETSAPPE and formation of AHPEPED at 254 nm and 280 nm are given in Table I. The photolytic decomposition of AETSAPPE in water was also accomplished by sensitization ( x =366 nm) with (4-benzoylbenzyl) trimethylammonium chloride (BTC), a water soluble benzophenone type triplet sensitizer. The quantum yield for the sensitized disappearance (Table I) is comparable to the results for direct photolysis (unfortunately, due to experimental complications we did not measure the quantum yield for AHPEPED formation). These results indicate that direct photolysis of AETSAPPE probably proceeds from a triplet state. 

The photochemical and thermal transformations of 5-methyldihydro-thiazolo[3,2-a]pyridinium-8-olate (515) have been investigated. Irradiation using a Hanovia mercury lamp and Pyrex filter gives the isomeric pyridone 516 (4%). When a Rayonet reactor was used, a product which appears to be the valence tautomer 517 (6%) was isolated. Further irradiation of 517 gave... 

Mechanistic Experiments. Sample solutions of [Mo -CsHs ] and [Mo(r75-C5H5)2D2] were prepared by distilling appropriate degassed solvent into Schlenk tubes that contained the complex. Tne sample solutions were subjected to short-term photolysis (<5 min) in a 350-nm Rayonet reactor. The solutions were frozen immediately after photolysis, and the mass spectrum of the gases above the frozen solutions was recorded. 

In contrast, in the photolysis of3,6-diphenylpyridazine-N-oxide 28 (R1 = R2 = Ph), a mixture of 3-benzoyl-5-phenylpyrazole 31 and 2,5-diphenylfuran 32 is formed. Diazoketone 29 (R1 = R2 = Ph) undergoes two competing reactions (i) thermal internal cyclization into the pyrazole 31 or (ii) photoinduced formation of a carbene leading to the final furan 32 (Scheme 12.9) therefore, the product distribution depends heavily on the reaction conditions. Thus, the formation of pyrazole 31 (75%) is favored over that of furan 32 (3%) by irradiation in acetone in a Rayonet reactor equipped with lamps irradiating at 350 nm. On the other hand, by irradiation with a Hanovia immersion lamp the yield of 31 decreases to 27%, whereas the yield of 32 increases to 67%. Moreover, the exclusive formation of the furan derivative 32 (43%) was observed by irradiation in the Rayonet reactor at low temperatures (—65 °C) [27]. 

For example, irradiation of ( )-iV-isopropyl-5-phenyl-4-pentenamine (0.01 M in acetonitrile purged with nitrogen) in a Rayonet reactor fitted with RPR 3000 lamps for 15 minutes (>95% conversion) results in the formation of A -isopropy 1-2-phenyl piperidine (65% yield) and 5-phenyl-4-pentenal (15%), whereas irradiation of the A-Zert-butyl compound resulted in quantitative formation of the imine28. cis Selective N-D addition was observed in the cyclization of (ZO-Af-deuterio-Af-methyl-S-phenyl-d-pentenamine [( )-l], but from the (Z)-isomer [(Z)-l] the cis/trans ratio was 3 1 28,66, since rotational equilibration of the biradical intermediate is faster than cyclization. 

An MeCN soln of 3-(l-naphthyl)-3ff-diazirine (0.02 M) containing acrylonitrile (O.l-l.OM) was degassed by three frecze-pump-thaw cycles under vacuum, sealed in a Pyrex tube. The tube was then irradiated for 2 h in a Rayonet reactor (350-nm lamps). The mixture was analyzed by GC and the products were isolated by MPLC, eluting with EtOAc/hexane (flow rate 4 mL/min). The stereoisomeric cyclopropanes were solids mp 84.5-85.5°C and mp 80-81 "C. 

The olefinic aldehyde 6a (58 mg, 0.26 mmol) and 4-toluenesulfonohydrazide in dry benzene (25 mL) was placed in a 5-mL flask equipped with a Dean-Stark water separator. The mixture was refluxed under dry Nj for 5 min. The solvent was removed and replaced by dry THF (2.5 mL) and 2 M BuLi in hexane (0.13 mL, 0.26 mmol) was added to the stirred solution. After 30 min the solvent was removed and the residual lithium salt of the tosylhydrazone 6b was heated slowly under reduced pressure (0.25 Torr). Between 120°C and 140°C the 4,5-dihydro-3/f-pyrazole 7 was collected as a colorless oil yield 50 mg (81% based on the aldehyde) nl 1.5042 [a] -I-95 (c = 1.0, CHCI3). A solution of the 4,5-dihydro-3i/-pyrazole 7 in Et20 (35 mL) was irradiated in a Rayonet reactor using 3500 A lamps and a Pyrex filter for 1 h. Removal of the solvent followed by distillation (airbath temperature, 80 °C) of the residual oil under reduced pressure (0.3 Torr) afforded pure (— )-cyclocopacamphene (8) yield 30 mg (93%) [a]o — 42 (c = 1.1, CHCI3). 

Experimental details.619 Hexane solutions of a styrylamine (106 or 108 0.01 m) in Pyrex (transparent over 280 nm) test-tubes were irradiated to >95% conversion (GC) under nitrogen using a Rayonet reactor fitted with 16 lamps (21 W /.in 300 nm Figure 3.10). Products were isolated in >80% chemical yield by either preparative... 

Experimental details.1348 1,4-Diiodocubane (494 0.2 mmol) suspended in dry methanol (6.0 ml) in a quartz tube equipped with a magnetic stirrer was irradiated in a Rayonet reactor equipped with 16 low-pressure mercury lamps (1 = 254 nm) (Figure 3.10) under a nitrogen atmosphere at 40 °C. About 32% monosubstituted 1-iodo-4-methoxycubane was detected by GC after 6h. Further irradiation gave a significant production of 1,4-dimethoxycubane (495 50%). 

Differences are observed in the photochemistry of Fe(C0)s adsorbed on silica and on porous Vycor. Irradiation of Fe(C0)s on Vycor at 350, 310, or 254 nm in a Rayonet reactor ( 1 mW/cm ) or with a frequency-tripled Nd YAG laser ( 400 mJ/cm - pulse) at Fe(C0)s loading levels of <10 mol/g results in formation of a species assigned as the oxidative addition product of photochemically-produced Fe(C0)4 with surface silanol groups and with chemisorbed... 

Ultraviolet irradiation of a powdered crystalline sample of 2(2,3- bis(4-methyl-enethiopyridyl)naphthalene, 2)-2(fumaric acid, 1) using 300 nm light (Rayonet reactor) for 10 days produced rcll-, 2,3,4-telracarboxylic acid 3 in 70% yield. 

A solution of 0.85 g (5.18 mmol) of 1.1.15b, 1.4 g (13.85 mmol) of triethylamine (2.5 eq.) and 100 )iL of decane in 20 nfL of dry acetonitrile was degassed by argon bubbling and distributed among 10 mL Duran glass tubes. After purging the tubes with argon for 1 min, they were sealed and irradiated for 120 h in a Rayonet reactor fitted with 300 nm lamps and a merry-go-round inset. The solvent was evaporated and purification by HPLC (cyclohexane/ethylacetate 93 7) yielded 0.352 g (41%) of 1.1.15c. 

In the di-7C-methane rearrangement example presented by M. Demoth the normal equipment of preparative laboratories is used, i.e. the suspension of chiral crystals ate irradiated in a Rayonet reactor leading to two isomers both in optically pure form. 

The photoreactions are carried out in 50-100 mL of 1,2-dimethoxyethane or cyclohexane solutions, flushed with Ar (15 min) prior to irradiation, with 0.1 M enone and 0.5 M 2-trimethylsilyloxy-l.3-butadiene reaction temp 8-10°C (water-cooled reaction vessel) reaction time 40-48 h. The reactions are run in a Rayonet reactor equipped with RPR 3000- (quartz vessel used) or —3500 A lamps (Pyrex vessel used) and monitored by GC and TLC. Purification and separation of the product mixtures are performed by flash chromatography (silica gel, 50-fold). 

Naphthalene (3). To a solution of 1-bromonaphthalene 1 (278 mg, 1 mmol) in monoglyme (3 mL) in a quartz tube with magnetic stirrer was added NaBH4 (1.9 g) and under Ar were added TTMSS 2 (23.8 mg, o.l mmol) and p-methoxybenzoyl peroxide. The reaction mixture was photolyzed at 254 nm in a Rayonet reactor. GC analysis yield 91%. 

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