Ethanol, irradiation

Substitution of quinoxaline takes place at C-2 when it is irradiated in ether, methanol, or ethanol. Irradiation of quinoxaline in acidified methanol furnishes 2-methylquinoxaline, and the reaction is suggested to go through a pathway involving electron transfer from the solvent to an excited state of the protonated quinoxaline (Scheme 5). Irradiation of quinoxaline under aerobic conditions in acidic aqueous solution leads to the formation of 5-hydroxyquinoxaline. ... 

However, the most striking Item In the Irradiation In alcoholic solvents Is the production of a number of toxisterols that arise through the participation of solvent molecules. The quantitatively most Important ones appear to be alcohol addition products, Isolated from methanol as well as from ethanol Irradiation mixtures (51). They were called toxlsterol Bl, B2, and B3. 

Ethanol/irradiation 1,2-Diamines from azomethines Dimerization... 

A soln. of the startg. 3-arylidenesuccinimide in 95%-ethanol irradiated ca. 24hrs. 

Selective reduction. A soln. of l,3-diphenyl-2-thioparabanate in abs. ethanol irradiated 15 hrs. with a 200 w. high-pressure Hg-arc under Ng l,3-diphenyl-2-... 

A suspension of potassium methyl benzoate tosylhydrazone in abs. ethanol irradiated at room temp, until gas evolution has ceased after 2 hrs. -> benz-... 

An ethanolic soln. of NaBH4 added rapidly by syringe at 15° to the startg. m. and 0.1-0.3 equivalent trimethyltin chloride in air-free abs. ethanol, irradiated 20 min. with a 100 w. Hg-flood-lamp, then oxalic acid added (to convert any trimethyltin hydride to the tin ester)... 

Benzenediazonium o-carboxylate in ethanol irradiated 0.5 hr. under Ng with the Pyrex-filtered light of a high-pressure Hg-lamp benzoic acid. Y 92.5%. -88.6% salicylic acid can be obtained by thermal decomposition in water. M. Kato, T. Tamano, and T. Miwa, Bull. Chem. Soc. Japan 48, 291 (1975). 

Azidocaffeine in dry ethanol irradiated 1.5 hrs. with the Pyrex-filtered light of a 450 w. Hanovia high-pressure Hg-lamp 8-amino-7-ethoxymethyltheo-phylline. Y 83%. F. e. s. D. R. Sutherland and J. Pickard, J. Heterocyclic Chem. 11, 457 (1974). 

Alkoxyazepines. A soln. of methyl o-azidobenzoate in ethanol irradiated with the Pyrex-filtered light of a 125 w. medium-pressure lamp -> 2-ethoxy-3-methoxy-carbonyl-3H-azepine. Y 67%. F. e. s. R. K. Smalley, W. A. Strachan, and H. Suschitzky, Synthesis 1974, 503. 

Wynberg described the photolysis of some pyridinecarboxylic acid derivatives. 3,5-Dicarbethoxy-2,4,6-trimethylpyridine (X-198) gave 3,5-di-carbethoxy-2,4,6-trimethyl-l, 4-dihydropyridine (X-199) and 3-carbethoxy-2,4,5-trimethylpyrrole (X-200) upon irradiation in ethanol. Irradiation of the 4-desmethyl derivative of X-198 in methanol afforded only reduction products or those of addition of solvent at the 2- or 4-positions. 

Benzyl esters can be efficiently cleaved by high-energy electron irradiation.— E A soln. of benzyl butyrate in ethanol irradiated under argon with 2-m.e.v. electrons butyric acid. Y 72%. F. e. and limitations s. A. Mac Lachlan, J. Org. Ghem. 29, 1598 (1964). 

Methyl dehydroursolate acetate in ethanol irradiated in a Pyrex-glass flask under Og-free Ng over a bare 125 w. Hg-arc lamp until UV-spectroscopy shows the band at 260 mju having f/> 10 000 and that at 240 m having f/ 8000, then refluxed 2 hrs. under Ng methyl pyrophotodehydroursolate acetate. Y 57 to 75%. R. L. Autrey et al., Soc. 1961, 3313. 

Figure 2. Spectral changes upon irradiation (254 nm, Hg lamp) of 2.6 10 M solution of 4-azidopyridinium hydrochloride in ethanol, irradiation time, s, (7) - (7) 0,60, 120,180, 300, 420, 1020 light intensity 8.7310 ° Emstemcm s [27...

A soln. of 2,3-dihydro-5,6-diphenylpyrazine in abs. ethanol irradiated with a Pyrex-filtered high-pressure Hg-vapor lamp until no more startg. m. can be detected by spectroscopy l-methyl-4,5-diphenylimidazole. Y 75%. F. e. s. P. Beak and J. L. Miesel, Am. Soc. 89, 2375 (1967). 

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