Irradiation acetonitrile

Normally, the reactions listed in Table I were carried out by irradiating acetonitrile solutions of polyoxometalate catalyst and substrate at 25 C. Deviations from these experimental conditions are noted in Table I. 

Irradiation of ethyleneimine (341,342) with light of short wavelength ia the gas phase has been carried out direcdy and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, / -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified ia a fast flow photoreactor iacluded hydrocyanic acid and acetonitrile (345), ia addition to those found ia a steady state system. The reaction of hydrogen radicals with ethyleneimine results ia the formation of hydrocyanic acid ia addition to methane (350). Important processes ia the photolysis of ethyleneimine are nitrene extmsion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an iatermediate ia the photolytic formation of hydrocyanic acid from acetylene and ammonia ia the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

The solvent is then evaporated, and the unconverted sterol is recovered by precipitation from an appropriate solvent, eg, alcohol. The recovered sterol is reused in subsequent irradiations. The solvent is then evaporated to yield vitamin D resin. The resin is a pale yeUow-to-amber oil that flows freely when hot and becomes a brittie glass when cold the activity of commercial resin is 20 30 x 10 lU/g. The resin is formulated without further purification for use in animal feeds. Vitamin D can be crystallized to give the USP product from a mixture of hydrocarbon solvent and ahphatic nitrile, eg, benzene and acetonitrile, or from methyl formate (100,101). Chemical complexation has also been used for purification. 

Oxidopyridazinium betaines isomerize photochemically into pyrimidin-4(3H)-ones (33). Irradiation of 3-oxidopyridazinium betaine or 1-oxidophthalazinium betaine in water affords similarly the corresponding pyridazin-3(2H)-one (35) and phthalazin-l(2H)-one derivative (37). However, photolysis in acetonitrile affords stable diaziridines (34) and (36) which can be converted in the presence of water to the final products (35) and (37) (Scheme 12) (79JCS(P1)1199). 

Irradiation of 3,5-disubstituted isoxazoles in alcoholic solvents gave reaction products such as acetals incorporating the reaction solvent. The use of triethylamine in acetonitrile media produced ketene-aminals by reductive ring cleavage. The reductive ring cleavage product was also obtained by irradiation of the isoxazole in alcohol in the presence of copper(II) salts (Scheme 3) (76JCS(P1)783). 

The rearrangement of phenyl- er -butyl nitrone to the isomeric oxazirane (9) occurred in 95% yield on irradiation in acetonitrile for 2 hr. Because 2-ieri-butyl-3-phenyloxazirane (9) can be reconverted into the more stable nitrone, the photochemical reaction involves the conversion of radiation energy into chemical energy. 

A similar irradiation of imide 9 in acetonitrile gives a mixture of ethyl 4,5-bis(ethoxy-carbonylamino)-l//-l,2-diazepine-l-carboxylate (10) and the isomeric ethyl 5,6-bis(ethoxycar-bonylamino)-l/f-l,2-diazepine-l-carboxylate (11) in the ratio 6 1. In contrast, when the irradiation is carried out in dichloromethane, the ratio is reversed to 1 2.5.81... 

Spanish researchers [32] also noted a considerable improvement upon sonica-tion of Diels-Alder reactions of l-dimethylamino-3-methyl-l-azadiene 44 with a variety of electron-deficient dienophiles by using diene as solvent or in acetonitrile (Scheme 4.9). Ultrasound irradiation which allows mild reaction conditions gave good to excellent yields. 

Photolysis of several 2-azidophenazines has been shown to afford quinoxahnes. Thus irradiation of 2-azidophenazine (576, R = H) in cyclohexane or acetonitrile gave, among other products, 3-(2-cyanovinyl)-2-quinoxalmecarbaldehyde (577) in <17% yield and irradiation of 2-azido-l-methoxyphenazine in degassed benzene or acetonitrile gave, among other products, a separable mixture of cis- and frawi-isomers of methyl 3-(2-cyanovinyl)-2-quinoxalinecarboxylate (578), each in low yield. 3 ... 

When position 6 on the 2-quinolone is blocked, bromination takes place selectively at the 3-position. Thus, microwave irradiation of 45 in acetonitrile at 150 °C for 50 min afforded the 3-bromo-quinolin-2(lff)-one 46 in 87% yield (Scheme 12). 

Irradiation of substituted a-dehydrophenylalanine 74 in acetonitrile gives isoquinoline 75 as a major product <96TL(37)5917>. 

Photoinduced oxidation of 1,4-dimethoxybenzene (DMB) and tetrahydrofuran (THF) by [Au(C N N-dpp)Cl]+ in acetonitrile upon UV/Vis irradiation have been observed. The time-resolved absorption spectrum recorded 12 (xs after excitation of [Au(C N N-dpp)Cl] with a laser pulse at 35 5 nm showed the absorption band of the DMB radical cation at 460nm, whereas upon excitation at 406 nm in the presence of THF, a broad emission characteristic of the protonated salt of 2,9-diphenyl-l,10-phenanthroline (Hdpp ) developed at 500 nm. 

The quantity R is proportional to the number of chain scissions per original macromolecule. For both PBS and PHS, for all solvents studied (1,4-dioxane, acetonitrile, chloroform, tetrahydrofuran, toluene and 2-butanone) the scattered light intensity decreases after irradiation. The amount of degradation R° for the same polysulfone is higher for solvents with larger yield of radicals. R° is larger for PHS than for PBS in the case of the solvents 1,4-dioxane and acetonitrile, which have the highest yield of radicals ... 

Fig. 6. UV-Vis absorption spectral change of trans-25 (0.126 mM) in acetonitrile under a nitrogen atmosphere upon photoirradiation with three bright lines (Amaj[ = 365, 436, and 546, nm) of a super-high-pressure Hg lamp. The spectra are depicted at 10 min intervals of photoirradiation. The irradiation with each bright line was continued for 30 min in ascending order of wavelength. (Reprinted with permission from Ref. 153.)...

Similar reaction pathways were recently shown to be available to the widely used chiral ligand l,l -binaphthol (BINOL) (138).87 Irradiation of BINOL in aqueous acetonitrile initiated ESIPT to the 4 -, 5 -, and 7 -ring carbons to give biaryl quinone... 

The photocycloaddition of maleic anhydride to acenaphthylene has been studied by Hartmann and Heine.(107a> Irradiation of acenaphthylene in the presence of maleic anhydride in light-atom solvents (dioxane, acetone, or acetonitrile) yields only dimers or copolymers of acenaphthylene. In heavy-atom solvents (dichloromethane, dibromomethane, or iodomethane), however, dimerization is suppressed and cycloaddition with maleic anhydride predominates ... 

Irradiation of 3-methoxyacetophenone in a solution of sodium cyanide in 5 1 acetonitrile-water is reported to result in (98). When the solvent is predominantly water, (99) and (100) are formed(146) ... 

Irradiation in polar solvents (acetonitrile, dimethylformamide, or methanol) leads to mixtures of (78) and (79) with the former predominating.<90 91) Nonpolar solvents (dioxane, benzene, or ethyl acetate) or the presence of benzophenone as sensitizer lead to a predominance of the anti isomer... 

Lehn and Ziessel166 have also developed systems for the photochemical reduction of C02. These systems are similar to those represented by Fig. 18. Visible-light irradiation of C02-saturated aqueous acetonitrile solutions containing Ru(bpy)2+ as a photosensitizer, cobalt(II) chloride as an electron acceptor, and triethyl-amine as a sacrificial electron donor gave carbon monoxide and... 

Photochemistry of Model Compounds. Preliminary photochemical studies have been carried out on l,3-diphenoxy-2-propanol (3)8 as a model compound for bisphenol A-epichloro-hydrin condensates 1. The utilization of 3 as a model compound for thermal degradation of 1 has been reported. Irradiation (254 nm) of 3 in acetonitrile (N2 purge) provides two major volatile products, which have been identified as phenol and phenoxyacetone (4), by comparison of retention times (gas chromatography) with known samples. A possible mechanism for... 

Irradiation Studies. Irradiation of l,3-diphenoxy-2-propanol (3), 0.01 M in acetonitrile, was conducted at 254 nm, utilizing a 2.5-W low pressure Hg immersion lamp (PCQ9G-1, Ultraviolet Products), and at wavelengths longer than 280vnm, utilizing a Hanovia 450-W high-pressure Hg immersion lamp (Type L) and 9700 Corex filter sleeve. Irradiation of 1,3-diphenoxy-2-methyl-2-propanol (5), 0.01 M in acetonitrile, was also conducted at 254 nm. 

For Schiff base being a derivative of gossypol and R-( I )-2-amino-3-benzyloxy-1-propanol, the conditions of the atropisomerisation were determined on the basis of the NMR spectra.37 The ratio of the diastereomers was established on the basis of the integrals of selected H signals (H-l and H-ll). The atropisomerisation of the gossypol Schiff base took place even if the samples were not exposed to the sunlight, however, this process was slower in the dark. The diastereopure Schiff bases were converted into a racemic mixture after ca. 12-14 h in the dark and ca. 3-3.5 h after irradiation of monochromatic light. The addition of a drop of water to acetonitrile solution accelerated the atropisomerisation. In this case, the 1 1 ratio of diastereomers was achieved after 45 min. The results obtained indicated that the atropisomerisation process cannot be considered as a simple photo-atropisomerisation. 

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