The photochemical reactivity of beta-lapachone (1), nor-beta-lapachone (2) and beta-lapachone 3-sulfonic acid (3) has been examined by laser flash photolysis. Excitation (lambda = 266 nm) of degassed solutions of , in acetonitrile or dichloromethane, resulted in the formation of detectable transients with absorption maxima at 300, 380 and 650 nm. These transients, with lifetimes of 5.0 micros, were quenched by beta-carotene at a diffusion-controlled rate constant and assigned to the triplet excited states of 1-3. Addition of hydrogen donors, such as 2-propanol, 1,4-cyclohexadiene, 4-methoxyphenol or indole led to the formation of new transients, which were assigned to the corresponding ketyl radicals obtained from the hydrogen abstraction reaction by the triplets 1-3 . In the presence of triethylamine it was observed the formation of the long-lived anion radical derived from , which shows absorption maxima at 300 and 380 nm. The low values observed for the hydrogen abstraction rate constants for the beta-lapachones 1-3 using 2-propanol and 1,4-cyclohexadiene as quenchers led us to conclude that their triplet excited states show pi pi* character.

alpha-Lapachone is a natural 1,4-naphthoquinone with promising biological activity. The fused dihydropyran ring present in its structure, acting as formal 2-alkoxy and 3-alkyl substituents to the quinone moiety, endows this compound with milder redox properties and lower toxicity, when compared with other bioactive 1,4-quinones. Its photochemistry, here reported, seems to originate from the triplet state, which shows pipi* character. Triplet quenching in acetonitrile solution with added hydrogen-atom donors such as 1,4-cyclohexadiene or 2-propanol is inefficient, independent of solvent polarity, and leads to formation of the semiquinone radical. With phenol and indole, quenching rate constants are two orders of magnitude higher, but smaller than the value for triethylamine. In the first two cases the semiquinone radical can be detected by laser flash photolysis and in the last case, the anion radical derived from alpha-lapachone is readily detected. The semiquinone radical can also be observed in the quenching of triplet alpha-lapachone by 2'-deoxyguanosine and by the methyl esters of L-tryptophan and L-tyrosine, whereas for L-cysteine methyl ester the quenching rate constant is very slow. Triplet alpha-lapachone is not quenched by thymine, thymidine, 2'-deoxycytosine or 2'-deoxyadenosine; this is probably due to its pipi* character and low energy, which prevents oxetane formation and triplet-triplet energy transfer, respectively. Steady-state photolysis of aerated solutions of these compounds in the presence of alpha-lapachone does not show evidence of decomposition, whereas similar experiments with 2'-deoxyguanosine result in efficient consumption of the nucleoside. Singlet oxygen is formed from triplet alpha-lapachone, and a quantum yield of 0.68 is measured.

The photochemical reactivity of b-lapachone (1), nor-b-lapachone (2) and 1,2-naphthoquinone (3) towards amino acids and nucleobases or nucleosides has been examined employing the nanosecond laser flash photolysis technique. Excitation (k = 355 nm) of degassed solutions of 1-3, in acetonitrile, resulted in the formation of their corresponding triplet excited states. Theseand their methyl esters new transients were formed in the quenching process, which were assigned to the corresponding radical pair resulting from an initial electron transfer from the amino acids or their esters to the excited quinone, followed by a fast proton transfer. No measurable quenching rate constants could be observed in the presence of thymine and thymidine. On the other hand, efficient rate constants were obtained when 1-3 were quenched by 2¢-deoxyguanosine (k q 10 9 L mol )1 s )1). The quantum efficiency of singlet oxygen ( 1 O 2 ) formation from 1 to 3 was determined employing time-resolved near-IR emission studies upon laser excitation and showed considerably high values in all cases (F D = 0.6), which are fully in accord with the pp* character of these triplets in acetonitrile.

Naftoimidazóis inéditos foram preparados por reação, ativada por microondas, entre paraformaldeído, β-lapachona (ou o-quinonas correlatas) e acetato de amônio suportado em montmorilonita k-10, ou em alumina básica. O uso do suporte básico forneceu os melhores rendimentos, superiores a 80%. Isso foi confirmado para a reação com β-lapachona e piperonal.New naphthoimidazoles were prepared by reaction, activated by microwave irradiation, between paraformaldehyde, β-lapachone (or related o-quinones) and ammonium acetate supported on montmorillonite k-10, or on basic alumina. Use of the basic support gave the best results, with yields above 80%. This was confirmed for the reaction with β-lapachone and piperonal.Keywords: imidazole, microwave, basic alumina, lapachone Introduction β-Lapachone (1a) is an ortho-naphthoquinone present in small amounts in trees of the Tabebuia species (Bignoniaceae), commonly called "ipê" or "pau d'arco" in Brazil. In addition, it can be obtained by the isomerization of lapachol, a quinone that is more abundant and more readily extracted from the same sources. The biological activities of these compounds and simple derivatives, have been investigated since the 1940's (anti-malarial 1 ) up to the present (anti-tumor, 2 anti-microbial, 3 anti-inflammatory 4 and anti-parasitic 5 ) and were recently reviewed. 6 The use of β-lapachone and some semi-synthetic derivatives as chemotherapic agents in the treatment of American trypanosomiasis (Chagas disease) has been investigated, 7 and five imidazole derivatives, prepared from this quinone and aromatic aldehydes, have shown expressive action over the tripamastigote form of Trypanosoma cruzi. 8,9 These imidazole derivatives were prepared by conventional methods. 9 As part of an ongoing study into the use of microwave activation and the use of supported reagents, in this case ammonium acetate, we investigated the preparation of the previously unknown simple imidazole derivatives of β-lapachone and related ortho-quinones with formaldehyde.Microwave activation has provided significant improvement on heterocyclic synthesis, 10 including imidazoles, with [11][12][13] or without support, 14,15 with reduction/ elimination of solvents, decreased reaction times and equal or improved yields. Results and DiscussionImidazole synthesis from α-diketones has a long history 16 and was initially plagued by low yields and by-products (such as oxazoles). Improvements occurred by the use of acidic conditions, e.g., glacial acetic acid reflux. 17 The availability of microwave technology for synthetic purposes has allowed the efficient preparation of 2,4,5-trissubstituted and 1,2,4,5-tetrassubstituted imidazoles. Further observed benefits, that were occasionally associated with solid supports such as silica, alumina, clays, amongst others, 11-13 included improved yields, and dramatic reductions in reaction time and quantities of solvent used (AcOH). 14,15 Interestingly, the best supports found in these studies were always the acidic in nature.Based on these findings, th...

The photophysics and photochemistry of the β-lapachone derived diphenyldihydrodioxin 3 were investigated using steady-state and time resolved techniques. Laser excitation of 3 leads to the formation of its cation radical 4 (absorption maxima at 410 and 450 nm and a lifetime of 10 μs), which was confirmed by its thermal generation employing tris(2,4-dibromophenyl)-aminium hexachloroantimonate (BAHA) as the electron acceptor. The cation radical 4 was also formed via the triplet excited state of 3 through a triplet sensitized process using benzophenone (ET = 69 kcal mol(-1)) as the sensitizer.

3, 3,9a,11,12, [1,4] Key indicators: single-crystal X-ray study; T = 120 K; mean (C-C) = 0.003 Å; R factor = 0.050; wR factor = 0.139; data-to-parameter ratio = 15.6.In the title dihydrodioxin, C 31 H 28 O 5 , the dioxane ring has a chair conformation, whereas each of the pyran and dioxine rings has an envelope conformation with methylene and quaternary C atoms, respectively, being the flap atoms. The phenyl rings are cis and form a dihedral angle of 82.11 (10) . The molecular structure is stabilized by C-HÁ Á ÁO contacts. In the crystal packing, supramolecular layers parallel to (101) are sustained by C-HÁ Á Á interactions. Related literature

Before the water problem that has taken place in Brazil and the need to reduce energy consumption in the country, it was thought the objective of this study was to evaluate the conditions of use and loss of potable water in the Baixada Fluminense, part of the metropolitan region of Rio de Janeiro (RMRJ), since it is the emergency waste reduction and the efficient and sustainable use of water. This exploratory study aims through a documentary approach, identify the number of water loss in the region. It proves that the loss in the region is more serious than in other states and that awareness campaigns should be implemented as local public policies. Also suggests that cleantech water use can be incorporated into the daily lives of homes and businesses enabling the reduction of water consumption.

Nos jogos de tabuleiro colaborativos os jogadores precisam utilizar estratégias para cooperar e vencer a partida juntos. A capacidade dos jogos de tabuleiro de abordar potencialmente qualquer temática, sua popularidade e seu cunho estratégico, os transforma em base para o desenvolvimento de metodologias ativas na Educação. Este artigo tem o objetivo mostrar a utilização de um jogo deste tipo, intitulado Salve a Terra!, focado em sustentabilidade ambiental. Os resultados indicam que o uso de jogos é recomendado para a criação de metodologias ativas de ensino.