Reactions of perfluorobenzocycloalkenes with ethyl cyanoacetate and methyllithium and some transformations of the products

Reactions of perfluorobenzocycloalkenes (Ar_FF) with methyllithium and ethyl cyanoacetate involved replacement of fluorine atoms in positions 3 and 4 of perfluorocyclobutabenzene, position 5 of perfluoroindan, and position 6 of perfluorotetralin by CH₃ and CH(CN)COOEt groups. Hydrolysis of the resulting esters Ar_FCH(CN)COOEt gave the corresponding perfluoroarylacetic acids Ar_FCH₂COOH which were converted into dichloroacetyl chlorides Ar_FCCl₂COCl by treatment with PCl₅. The reaction of Ar_FCCl₂COCl with SbF₅ produced trifluoromethyl derivatives Ar_FCF₃. Decarboxylation of Ar_FCCl₂COOH in DMF afforded dichloromethyl derivatives Ar_FCCl₂H which reacted with CsF on heating to form difluoromethyl analogs Ar_FCF₂H.     

Luminescent Properties of Metal Porphyrin Reduction Products

We have investigated the luminescent properties of -anions in Zn and Pd complexes of octaethylporphin and etioporphyrin, and also of protonation products of -dianions (-monoanions of phlorins). It is established that the quantum yield of luminescence of -anion radicals in Zn complexes amounts to 2.9·10^–4. The lifetime of the lower excited (doublet) state is estimated to be 120 ± 25 nsec. We failed to reveal the luminescence of -dianions. In reducing the Pd porphyrins into -anion radicals and -dianions, a loss of the luminescent properties is observed. However, the -monoanion of phlorin in Pd octaethylporphin luminesces. The Zn complex of the phlorin anion also has the same properties. The spectral properties of Zn and Pd phlorin anions are similar: a large Stokes shift is observed at room temperature; on decrease in the temperature to 77 K the fluorescence spectrum becomes narrower, the maximum of the spectrum shifts strongly to the blue region, and the quantum yield of luminescence increases. The special features of the spectral properties of phlorin anions are explained by conformation changes in the excited state. It is found that in a solution at room temperature Pd phlorin anions quench the phosphorescence of neutral Pd porphyrins.     

Study of Mn2+ and Fe2+ in the structure of monticellite by the electron paramagnetic resonance method

Journal of Structural Chemistry -     

Reaction of perfluorinated 1-ethyl-, 1,1-diethyl-, and 1,2-diethylcyclobutabenzenes with pentafluorobenzene in SbF<Subscript>5</Subscript>

Perfluoro(1-ethyl-1,2-dihydrocyclobutabenzene) reacts with pentafluorobenzene in SbF5 to give perfluoro(1-ethyl-2-phenyl-1,2-dihydrocyclobutabenzene). Analogous reaction of a mixture of perfluoro(1,1-diethyl-1,2-dihydrocyclobutabenzene) and perfluoro(1,2-diethyl-1,2-dihydrocyclobutabenzene) leads to the formation (after hydrolysis of the reaction mixture) of perfluorinated 7-phenyl-8,8-diethylbicyclo[4.2.0]octa-1,4,6-trien-3-one, 1,1-diethyl-2-(4-oxocyclohexa-2,5-dienylidene)-1,2-dihydrocyclobutabenzene, and 2-(pent-2-en-3-yl)benzophenone (from the 1,1-isomer) and perfluorinated (E)-1,2-diethyl-1-phenyl-1,2-dihydrocyclobutabenzene, 7,8-diethyl-8-phenylbicyclo[4.2.0]octa-1,4,6-trien-3-one, and 1-[2-(1-phenylprop-1-en-1-yl)-phenyl]propan-1-one (from the 1,2-isomer).     

Expansion of the pentafluorobenzene ring and other skeletal transformations in the reaction of perfluoro(1,2-diethyl-1-phenyl-1,2-dihydrocyclobutabenzene) with antimony pentafluoride

The reaction of perfluoro(1-phenyl-1,2-diethyl-1,2-dihydrocuclobutabenzene) with SbF5 at 20°C, followed by treatment of the reaction mixture with water gave perfluoro {4-[1-(2-propylphenyl)propylidene]-2,5-cyclohexadien-1-one} together with perfluoro[4b,10-diethylbenzo[a]azulen-7(4bH)-one] resulting from unusual expansion of the pentafluorobenzene ring to seven-membered ring. Analogous reaction at 90°C, apart from the above compounds, afforded perfluorinated 10-ethyl- and 3,10-diethylbenzo[a]azulen-6(10H)-ones via elimination of C₂F₅ group from the seven-membered ring or its migration to the benzene ring.     

New acid photogenerators based on thioxanthen-9-one sulfonium derivatives for detritylation in the oligonucleotide synthesis

Photochemical activity of a number of cationic thioxanthen-9-one derivatives for the formation of the trityl cation was studied, which resulted in the selection of compounds suitable for photodetritylation. 10-(4-Heptyloxyphenyl)-9-oxo-2-(N,N,N-triethylammonio)methyl-9H-thioxanthenium bis(hexafluorophosphate) and 2-methyl-, 2-(2-methyl-1-propanoyl-2-tosyl)-, 1-chloro-4-propoxy-, and 2,4-diethyl-10-(4-heptyloxyphenyl)-9-oxo-9H-thioxanthenium hexafluorophosphates were found to be photoactivators of detritylation of 5′-O-(4,4′-dimethoxytrityl)thymidine. The detritylation reaction is the most efficient in dichloromethane. 2,4-Diethyl-10-(4-heptyloxyphenyl)-9-oxo-9H-thioxanthenium hexafluorophosphate was used as a detritylation photoactivator in the oligonucleotide synthesis using an automated DNA synthesizer. The yield in the elongation step of the oligonucleotide chain was 98%.     

Polarized fluorescence of monoanions of Zn-octaethylphlorin

We investigate the luminescent properties (radiation spectrum, polarized spectrum) of the monoanions of Zn-octaethylphlorin, which is an intermediate product of the reduction, reaction of porphyrins. An oscillator model is presented that includes three electronic oscillators, with a long-wave one being oriented perpendicularly to the remaining two. The lifetime of the excited singlet state τ=30±15 nsec is estimated. Institute of Molecular and Atomic Physics, Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 329–332, May–June, 1997.