Reactivity of styrylmalonates as synthetic equivalents of Donor–acceptor cyclopropanes with aldehydes in the presence of BF3•Et2O
Donor–acceptor cyclopropanes (DACs), which can act as sources of 1,2- and 1,3-zwitterions in the presence of Lewis acids, are widely used in organic synthesis for the preparation of various carbo- and heterocyclic compounds, including natural compounds and their analogues. To date, many types of DACs reactivity have been identified. However, the chemistry of styrylmalonates (isomers of DACs, which can be easily generated from DACs) is almost undescribed and has a powerful synthetic potential. The use of styrylmalonates as synthetic equivalents of DACs allows us cardinally change the known reaction pathways of DACs. In this work, a new strategy for cascade assembly of substituted pyrenes based on the reactions of styrylmalonates with aldehydes in the presence of BF3•Et2O has been developed. Generation of formal 1,2-zwitterionic intermediates owing to complexation of dicarboxylate groups with BF3•Et2O is the driving force of the reaction discovered. This method makes it possible to assemble pyrenes or 5,6-dihydro-2H-pyran-2-ones in one synthetic stage from readily available starting compounds with high regio- and diastereoselectivity, and use these pyrenes in futher reactions. We’ve optimized conditions of the reaction and synthesized a number of various substituted pyrenes. Moreover, the reaction shows good results with various aromatic and heteroaromatic substituents. Pyrenes can be easily purified by crystallization. Every product was obtained selectively and determined by full set of physical-chemical methods, including X-ray analysis. 5,6-dihydro-2H-pyran-2-one skeleton is found in various natural compounds demonstrating a broad spectrum of biological activity, such as antiviral and antineoplastic.
Interaction of the unsaturated sulfones with azinium ylides
1. Introduction In Japan the energy self-efficiency is very low: only 6%. Hydrogen (H2) has been expected as a new and alternative energy source to imported one, such as petroleum resources. Now hydrogen energy comes into the practical use in the field of the fuel cell. Hydrogen must be extracted from other sources, for example, water, fossil fuel, and so on. Hydrogen is obtained from water by using electronic or thermal or photo energy in most cases, whereas it is well-known that hydrogen is given by the oxidation reaction of silicon in alkaline aqueous solution: Si + 2OH- + H2O → SiO32- + 2H2 Free silicon (Si) is not only used in the steel refining, aluminum-casting in the field of fine chemical industries but also is used as a material in semiconductor electronics. However, a lot of used silicon is thrown away as a waste, being not reused and recycled. In this study we try to apply a waste silicon to obtain hydrogen based on the above reaction. The purpose of the study is to develop a safe and convenient manufacturing method to generate hydrogen for an energy source of the fuel cell.
Plexiglas: from synthetic glass to cationic exchanging resin
Plexiglas is a macromolecule (poly-methyl-methacrylate) obtained by polymerization of the Methyl Methacrylate. Cation exchanging resins have acidic groups such as COOH (carboxyl) and SO3H (sulfonic) which fix metallic cations dissolved in water releasing an equivalent of protons through the following reaction: 2 RCOOH + Me2+ (RCOO)2Me + 2 H+ Regeneration is made treating the exhausted resin with diluted hydrochloric acid (HCl) which moves the equilibrium to the left. The aim of our research is to re-use the discarded Plexiglas by transforming it into a cationic exchanging resin. Alkaline hydrolysis transforms the COOCH3 group into COO– group; the obtained group is then transformed into COOH group by means of a treatment with HCl. After the alkaline hydrolysis spectra of the solid show the characteristic band of the asymmetric stretching of the COO– (1610-1550) at 1567 (1st experiment) and at 1555 (2nd experiment). Instead after the acidic treatment the spectra of the solid show that this band has disappeared. On the contrary the characteristic band of the OH stretching of the COOH group (3300-2500) at 3228 (1st experiment) and at 3200 (2nd experiment) appears. The water hardness, due to Ca2+ and Mg2+ ions, is studied to verify the capability of the obtained resin to capture these cations. For this purpose, some mineral water is percolated through the micro-columns. There are three experimental evidences to validate the hypothesis: EDTA molecule (Ethylene Di-amino Tetra-Acetic acid, disodium salt) to estimate hardness is not required The pH of the percolated water through the column decreases from 8 of the mineral water without any treatment, to 6.3 after the treatment as expected The spectrum recorded in the visible range of the percolated mineral water through the column plus EBT (Eriochrome Black T) indicator is the same as the spectrum obtained using de-ionized water plus the same amount of EBT In conclusion, the study has provided evidence that it is possible to convert Plexiglas into cationic exchanging resin.
Findings of new oscillations in BR reaction
The Briggs Rauscher reaction, i. e., BR reaction, which is one of the oscillation reactions, produces iodide ion and iodine repeatedly. Continual color changes of the solution from colorless to deep blue, and vice versa, are observed during the reaction due to the so-called “iodine test” reaction. In this work, we studied the effects of the presence of the redox active indicators on the oscillation behavior of the BR reaction. To the reaction mixture of KIO3, H2SO4, H2O2, C3H4O4, MnSO4, and starch, which are used for the general BR reaction as added a redox active reagent (indicator). Then, the changes in color and voltage of the reaction solution were recorded by a photosensor of the LEGO MINDSTORMS and a voltmeter using Pt electrodes. Under general reaction conditions, the oscillation reaction continued for ca. 5 minutes, including 18 times of oscillations. When an indicator, such as BTB, was added instead of starch to the reaction solution, splits of the voltage wave were observed, which should be a kind of new oscillation. Moreover, we found that the addition of K3[Fe(CN)6], which exhibits high redox activity, in the reaction solution instead of starch made the life-time and the numbers of the oscillation in the reaction greater by 3 times (14 min.) in time and more than 4 times (81 times) in the frequency. It’s also a kind of new oscillation. These results suggested that the oxidation-reduction reactions by the addition of ferricyanate ion effectively promotes the redox process of iodine and iodide ion. The experiments we wrote above were conducted without starch. Thus, as a reference, we conducted the same experiments under the presence of starch and got interesting results. We also studied the effects of K4[Fe(CN)6], suggeting that not only redox reaction between ferricyanide and ferrocyanide ion, but also the redox reaction with BR solution should occur in these reactions.