Photochemical reactions of some mono- and diketo derivatives of adamantane in various solvents

Adamantanes are photoactive in the presence of CCl₄ and CDCl₃. The mechanism of their photolysis, involving the formation of singlet or triplet excited donor-acceptor complexes has been suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1833–1835, September, 1995.This work was partially financially supported by the Russian Foundation for Basic Research (Project No. 93-03-18102).     

Photochemical reactions of di(naphthyl-1-methyl)mercury in various solvents

It was found that the photolysis of di(naphthyl-1-methyl)mercury (1) gives 1,2-dinaphthylethane (2) in heptane and benzene solvents and 2 and 1-methylnaphthalene in isopropanol and acetonitrile. Irradiation of 1 in carbon tetrachloride gives 2 and ClHgCH₂C₁₀H₇ as primary reaction products, while the chloride is further photolyzed to 2. Quantum yields of the photolysis of 1 are high and equal to unity almost for all solvents. The chloride photodecomposition yield is an order of magnitude lower (0.1).     

Photochemical reactions of organomercury compounds in organic solvents

The quantum yields of photolysis of organomercury compounds in different organic solvents have been measured. It was shown that the quantum yields of photolysis of nitro derivatives of mercury compounds and the symmetric (methylnaphtyl)mercury compound are equal to unity. The photolysis of halo derivatives of benzylmercury proceeds with lower quantum yields as compared with photolysis of analogous dibenzylmercury derivatives. The quantum yields of photolysis of organomercury compounds are almost independent of the solvent.     

Photochemical reactions of 2,3-diphenylindoles

The UV irradiation of 2,3-diphenylindoles produces two photochemical reactions: a dehydrocyclization with formation of dibenzocarbazoles and a photo-oxygenation which yields benzophenones.Substituents on the 2,3-diphenylindole have a great influence on the reaction course and in most of the examples here studied only one product was formed.Some considerations about the excited states involved in these reactions are presented.     

Photochemical reactions of 7-aminocoumarins

The photochemical reactions of 4-methyl-7-diethylaminocoumarin with the dimethyl ester of acetylenedicarboxylic acid, diethyl ester of maleic acid, and N-phenylmaleimide in the presence of oxygen and acetophenone give products of the heterocyclization at C(₆) and C(₈) of coumarin fragment with participation of the diethylamino group. The stereochemical structure of the compounds synthesized was demonstrated using PMR spectroscopy. A mechanism was proposed for this reaction involving the formation of an -amino radical and its addition to the acetylene or olefin, accompanied by attack on the aromatic ring with subsequent aromatization.See [1] for Communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 30–36, January, 1989.     

Photochemical reactions of allylphenoxide anions

Photochemical behaviour of sodium allylphenoxides 1a–3a was compared with that of corresponding neutral allylphenols 1b–3b, and a striking difference was found in reactivity as well as in course of the reaction. Remarkably higher photoreactivity of allylphenoxide anions, especially that of o-allylphenoxide 1a, is ascribed to the efficiency of electron transfer. The characteristic reaction products derived only from the anions were as follows: (a) intramolecular cyclization products, indanols 9, from 2a, (b) rearranged reduction products 10 from both 2a and 3a, and (c) degradative methanol-adduct 11 from 3a. Methanol-adducts 7 and photo-reduction products 6 were formed in either case. In addition cyclization products with the participation of O atom, 4 and 5, were obtained from 1a and 1b. Occurrence of the di-π-methane rearrangement was restricted to the reaction of neutral species 1b–3b. A mechanism based on electron transfer in the excited state is suggested for the course of the photoreaction.     

Photochemical electron transfer reactions in alkylcobaloximes

It is shown that photolysis with visible light (λ > 420 nm) of any alkylcobaloxime procedes via a mechanism involving an initial electron transfer reaction from an equatorial ligand to the central metal to produce a cobalt(II) species which retains both original axial ligands. In a subsequent rearrangement of the equatorial ligand a hydrogen atom is ejected.     

A review of proton transfer reactions between various carbon-acids and amine bases in aprotic solvents

The subject of proton transfer between carbon acids and nitrogen bases in aprotic solvents is reviewed. Equilibrium and rate constants that characterize such reactions are most often determined utilizing UV-visible spectrophotometry. At ambient temperature reaction rates are sufficiently rapid that fast reaction methods, for example, the stopped-flow and temperature-jump techniques are required in many cases. Variation of the properties of the donor and acceptor reaction pairs enables electronic and steric effects upon thermodynamic and kinetic parameters of proton transfer to be assessed. Determination of the kinetic isotope effect (KIE), i.e. k(protium)/k(deuterium) led to the conclusion that, under certain circumstances and when the KIE is greater than seven, the proton undergoes reaction with a significant degree of quantum mechanical tunneling, consistent with a theoretical prediction advanced several decades earlier. In fact this aspect may be one of the most significant outgrowths of these studies. Many reactions have been characterized (by tunneling) but rarely are the reacting systems experimentally amenable to obtaining all the experimental criteria that support tunneling. Controversy that has arisen regarding treatment of experimental data and resulting conclusions from them is visited in this review. The structural nature of the product state of reaction is formulated based on spectroscopic evidence, in favorable cases, and probable structures of the transition state can be inferred.     

Photochemical electron transfer reactions of tirapazamine

The absorption and fluorescence spectra of 3-aminobenzo-1,2,4-triazine di-N-oxide (tirapazamine) have been recorded and exhibit a dependence on solvent that correlates with the Dimroth ET30 parameter. Time-dependent density functional theory calculations reveal that the transition of tirapazamine in the visible region is pi-->pi* in nature. The fluorescence lifetime is 98+/-2 ps in water. The fluorescence quantum yield is approximately 0.002 in water. The fluorescence of tirapazamine is efficiently quenched by electron donors via an electron-transfer process. Linear Stern-Volmer fluorescence quenching plots are observed with sodium azide, potassium thiocyanate, guanosine monophosphate and tryptophan (Trp) methyl ester hydrochloride. Guanosine monophosphate, tyrosine (Tyr) methyl ester hydrochloride and Trp methyl ester hydrochloride appear to quench the fluorescence at a rate greater than diffusion control implying that these substrates complex with tirapazamine in its ground state. This complexation was detected by absorption spectroscopy.     

Photochemical reactions of 7-aminocoumarins.

A number of 3-aryl-4-methyl-7-diethylaminocoumarins were obtained as a result of the photolysis of 3-iodo-4-methyl-7-diethylaminocoumarin in the presence of benzene, chlorobenzene, fluorobenzene, benzonitrile, toluene, and diphenyl ether. On the basis of an analysis of the PMR spectra it was established that photosubstitution leads to o- and p-isomeric products. The mechanism of the reaction was studied.See [1] for Communication 7.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1172–1176, September, 1990.     

Photochemical incorporation of protic solvents by open chain olefins

Irradition of methyl styryl sulphoxide dissolved in MeOH, EtOH, or AcOH induces the photochemical polar addition of the solvents to afford the product, PhCH(OR)CH₂SOMe, where R is Me, Et, or Ac. By-products are the corresponding sulphides, PhCH(OR)CH₂SMe, and methyl styryl sulphide. Similar adducts of protic solvents are produced upon irradiation of certain vinylic sulphides, methyl phenethynyl sulphide, as well as appropriately substituted propenylbenzenes including o-anethole, o-anol, and o-propenylaniline in soln.     

Photochemical reactions of aqueous plutonium systems

Photochemical effects on four aqueous plutonium perchlorate solutions have been observed and reported. The photochemical reduction of PuO₂²⁺ and of Pu⁴⁺ to Pu³⁺ have been observed, and the quantum yields were determined to be 0·02 and 0·03, respectively. A reversible photochemical shift in the equilibrium of the Pu⁴⁺ disproportionation was observed, and the equilibrium coefficient increased by a factor of three when the sample was irradiated. Light has been observed to increase the rate and extent of depolymerization of Pu(IV) polymer.     

Photochemical mediated reactions in five-membered O-heterocycles synthesis

Photochemical mediated synthesis in organic chemistry is a highly expanding area. This is a widely exploited area of research for the construction of new pharmaceutically significant heterocycles. Recently many reports appeared for the synthesis of heterocycles photochemically due to a wide range of biological activities associated with them. In this article, I have described the synthesis of a number of oxygen-bearing five-membered heterocycles.