Medium immersion well

The apparatus is dried in an oven at 140° overnight and cooled under nitrogen or argon prior to the irradiation. A Vycor filter sleeve and a 450-watt medium-pressure mercury lamp are placed in the immersion well. The Vycor filter, the quartz immersion well (catlog No. 19434), the 450-watt mercury lamp (catalog No. 679A36), and the requisite transformer are all available from Hanovia Lamp Division, Canrad-Hanovia Inc., 100 Chestnut Street, Newark, New Jersey 07105. 

The checkers employed a Hanovia 450W medium-pressure mercury arc lamp with an uranium glass filter, a Pyrex immersion well, and a 1-L irradiation vessel (all available from Ace Glass). 

The photochemical step could also be accomplished by adding Mo(CO)e, EtjN and EtgO to a photochemical immersion well, and irradiating under an inert atmosphere with a Hanovia medium pressure 450W mercury vapor lamp for 20-30 min. Commercially available immersion wells generally require > 800 mL of solvent in order to work effectively (so that the solvent is level with the lamp), and the submitters have found that the more concentrated solution reported here (ca. 450 mL) is more effective. 

To a solution of the diene (1 -2 g) in anhyd Et20 (140 mL) was added CuOTf (1 -2 moI%). This homogeneous solution was irradiated under an atmosphere of N2 with a medium-pressure Hg lamp through a water-cooled quartz immersion well until disappearance of the starting diene (15 40 h). After completion of the reaction, the Et20 solution was poured into a mixture of crushed ice and 30% NH4OH (100 mL) and shaken well. The two layers were separated and the deep blue aqueous layer extracted with Et,0 (2 x 50 mL). The combined Et,0 extracts were washed with brine and dried (MgSO+). Et,() was removed by rotary evaporation and the residual oil distilled. 

The reaction was carried out in an immersion-well photoreactor with a medium-pressure. 80-W Hg lamp in a water-cooled double jacket (quartz and Simax glass, sintered-glass inlet at the bottom of the reactor), and equipped with a dry icc cooled spiral cooler with an hydraulic seal. A mixture of 3,4,4-trifluoro-5.5-dimethyl-4.5-dihydrofuran-2(3//)-one (3 67 mg, 40 mmol) and solvent (2 mol) was irradiated for 10 h at 18-20 C in a stream of argon. The low-boiling part of the mixture was fractionally distilled off and the product was isolated by preparative GC (polybutane-1,4-diol succinate, 500 cm, 160-200 C) vicld 50-65%. 

Figure 1.9 The circulation ofa solution around an immersion well fitted with a medium-pressure mercury lamp.

A. 3-(l-Hyivoxybutyl)-l-methyl-pyrvole (1). A photochemical quartz immersion well (220 mu length) (Note 1) equipped with 450-watt Hanovla medium pressure mercury lamp and a Vycor filter, cooled with water, 1s used. To a 125-mL Pyrex reaction vessel (230 mn long, 64 mm i.d.) equipped with a gas inlet and outlet, is added 60 rriL (55 g, 0.676 mol) of 1-methylpyrrole (Note 2)... 

The irradiation light source is a Hanovia 450 W medium-pressure Hg vapour lamp placed in a quartz immersion well. The reaction solution is contained in a 150 ml quartz semicircular flask mounted as closely as possible to the immersion well. No light filter is used. The entire apparatus is immersed in a large Dewar flask charged with dry ice-isopropanol with the bath temperature maintained between —60 and —40°C during irradiation. 

A solution of 9-diazo-9f/-fluorene (200 mg, 1.0 mmol) in styrene (20 mL, 18.2 g, 0.17 mol) was placed in a Pyrex outer jacket surrounding a quartz immersion well. After being purged with a dry N2 gas stream for 2 h, the solution was irradiated for 24 h with a Hanovia 450-W medium-pressure Hg lamp placed within the water-cooled immersion well and shielded by a cylindrical uranium glass filter to remove all wavelengths below 330 nm. After removal of excess styrene in vacuo, yellow crystals were observed. Purification by chromatography on a column of silica gel (230-400 mesh) with 20% benzene in hexane as eluant gave 246 mg (92%) of product mp 127 C. 

Experimental details liquid-state photolysis,957 Acetonitrile solutions of 279c (0.07 m) in Pyrex tubes were purged with nitrogen for 15 min and then irradiated with a medium-pressure mercury lamp (450W) in a water-cooled Pyrex (2lrr>280nm) immersion well (Figure 3.9) at 20 °C for several hours. The chemical yields of 280 and 281 were 53% and 44% (GC), respectively. 

Experimental details solid-state photolysis 957 A crushed crystalline ketone (279a or 279b) ( 5 mg), suspended in hexane (3 ml), was placed between Pyrex microscope slides, sealed in a polyethylene bag under nitrogen and irradiated with a medium-pressure mercury lamp (450 W) at a distance of 10 cm from a water-cooled Pyrex immersion well (Figure 3.9) at either 20 or — 20 °C (cryostat ethanol bath). The product, a chiral organic salt, was derivatized to the corresponding methyl ester by treatment with excess diazomethane and purified by column chromatography. 

Small (1-5 g) scale UV photolysis of air sensitive compounds can be performed in quartz Schlenk tubes, or in conventional Schlenkware with the use of a UV transparent quartz stopper. The latter apparatus is easily adapted to low temperature irradiations. Large scale (10-50 g) UV photochemical reactions use quartz immersion well reactors. Medium pressure Hg-arc lamps are the preferred radiation sources for synthetic applications. ... 

Figure 1 An immersion well apparatus consisting of a cylindrical 450 Watt Hanovia medium pressure arc lamp in a water-cooled quartz well. The quartz well is shown surrounded by the Pyrex reaction flask.

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