Organic Preparations and Procedures International, 2020
Rishitinol (Scheme 1, 5), a phytoalexin sesquiterpene, is produced in stressed white potato (Sola... more Rishitinol (Scheme 1, 5), a phytoalexin sesquiterpene, is produced in stressed white potato (Solanum tuberosum) as a response to infection by Phytophtora infestans fungus. 1 , 2 It was isolated fro...
ABSTRACT Keto–enol tautomeric equilibrium and the mechanism of thermal conversion of 2- and 4-hyd... more ABSTRACT Keto–enol tautomeric equilibrium and the mechanism of thermal conversion of 2- and 4-hydroxyacetophenone in gas phase have been studied by means of electronic structure calculations using density functional theory (DFT). A topological analysis of electron density evidence that the structure of keto and enol forms of 2-hydroxyacetophenone are stabilised by a relatively strong intramolecular hydrogen bond. 2- and 4-hydroxyacetophenone undergo deacetylation reactions yielding phenol and ketene. Two possible mechanisms are considered for these eliminations: the process takes place from the keto form (mechanism A), or occurs from the enolic form of the substrate (mechanism B). Quantum chemical calculations support the mechanism B, being found a good agreement with the experimental activation parameters. These results suggest that the rate-limiting step is the reaction of the enol through a concerted, non-synchronous, semi-polar, four-membered cyclic transition state (TS). The most advanced reaction coordinate in the TS is the rupture of O1···H1 bond, with an evolution in the order of 79.7%–80.9%. Theoretical results also suggest a three-step mechanism for the phenyl acetate formation from 2-hydroxyacetophenone.
Organic Preparations and Procedures International, 2019
We recently reported the successful introduction of the isopropyl group into the aromatic ring of... more We recently reported the successful introduction of the isopropyl group into the aromatic ring of 5-methoxy-1-tetralone and 7-methoxy-1-tetralone using 2-propanol (2PrOH) and polyphosphoric acid (PPA). These results have now prompted us to carry out the isopropylation of 6-methoxy-1-tetralone (1) as a possible route to 5-isopropyl-6methoxy-1-tetralone (3) and 7-isopropyl-6-methoxy (4) respectively (Scheme 1). The tetralone 3 and tetralone 4 are potential intermediates for the preparation of the bioactive phenolic diterpenes Totarol 5 and Sempervirol 6 respectively (Scheme 1). These compounds were originally isolated from the wood of Tetraclinis articulata and from the resin of Cupressus sempervirens respectively. Recently Totarol 5 has also been discovered in the Chilean Podocarpaceae, juniperus and Mediterranean propolis. It has been approved for use as an antimicrobial additive in toothpaste and acne treatments and for prophylaxis of schistosomiasis and fascioliasis in humans, sheep, goats and cattle. The antibacterial activity of Totarol 5 and anthelmintic activity of Sempervirol 6 are well documented. In the event, to a mixture of commercially available PPA and 2-PrOH heated to 75–80 C we added the tetralone 1 and the mixture was heated for 5 h to obtain a viscous material. This contained a mixture of recovered tetralone 1 and three products of different intensities (but distinct Rf values) as evidenced in thin layer chromatography. Chromatographic purification afforded tetralones 2, 3 and 4 in yields of 10%, 20% and 32% respectively (Scheme 1). The structures of the tetralones 2, 3 and 4 were ascertained by H NMR and C NMR spectroscopy (see Experimental Section). When the isopropylation experiment was carried out by heating the reaction mixture at 100–110 C for 10h, the tetralone 4
2014 11th International Conference on Electrical Engineering, Computing Science and Automatic Control (CCE), 2014
Transparent and conductive Indium-doped zinc oxide (ZnO:In) thin films were deposited on glass su... more Transparent and conductive Indium-doped zinc oxide (ZnO:In) thin films were deposited on glass substrates by the ultrasonic spray pyrolysis technique. ZnO:In thin films were prepared by mixing 0.2M zinc acetate and 0.2M indium sulphate dissolved in a mixture of water, acetic acid and methanol. Indium sulphate which acts as the In source was chosen at three different atomic concentrations, namely, 1, 2, and 3 at. % and the films were deposited at a temperature ranging between 385 °C and 430 °C. The dependence of the electrical and optical properties on the substrate temperature and the dopant concentration was studied. Electrical resistivity as low as 1.6×10-3 Ωcm, electron mobility around 11 cm2/(V-s), carrier concentration in the range 4.96-8.98 ×1020 cm-3, and an optical transmittance of about 80 % was achieved for 3 at. % ZnO:In thin films.
Organic Preparations and Procedures International, 2020
Rishitinol (Scheme 1, 5), a phytoalexin sesquiterpene, is produced in stressed white potato (Sola... more Rishitinol (Scheme 1, 5), a phytoalexin sesquiterpene, is produced in stressed white potato (Solanum tuberosum) as a response to infection by Phytophtora infestans fungus. 1 , 2 It was isolated fro...
ABSTRACT Keto–enol tautomeric equilibrium and the mechanism of thermal conversion of 2- and 4-hyd... more ABSTRACT Keto–enol tautomeric equilibrium and the mechanism of thermal conversion of 2- and 4-hydroxyacetophenone in gas phase have been studied by means of electronic structure calculations using density functional theory (DFT). A topological analysis of electron density evidence that the structure of keto and enol forms of 2-hydroxyacetophenone are stabilised by a relatively strong intramolecular hydrogen bond. 2- and 4-hydroxyacetophenone undergo deacetylation reactions yielding phenol and ketene. Two possible mechanisms are considered for these eliminations: the process takes place from the keto form (mechanism A), or occurs from the enolic form of the substrate (mechanism B). Quantum chemical calculations support the mechanism B, being found a good agreement with the experimental activation parameters. These results suggest that the rate-limiting step is the reaction of the enol through a concerted, non-synchronous, semi-polar, four-membered cyclic transition state (TS). The most advanced reaction coordinate in the TS is the rupture of O1···H1 bond, with an evolution in the order of 79.7%–80.9%. Theoretical results also suggest a three-step mechanism for the phenyl acetate formation from 2-hydroxyacetophenone.
Organic Preparations and Procedures International, 2019
We recently reported the successful introduction of the isopropyl group into the aromatic ring of... more We recently reported the successful introduction of the isopropyl group into the aromatic ring of 5-methoxy-1-tetralone and 7-methoxy-1-tetralone using 2-propanol (2PrOH) and polyphosphoric acid (PPA). These results have now prompted us to carry out the isopropylation of 6-methoxy-1-tetralone (1) as a possible route to 5-isopropyl-6methoxy-1-tetralone (3) and 7-isopropyl-6-methoxy (4) respectively (Scheme 1). The tetralone 3 and tetralone 4 are potential intermediates for the preparation of the bioactive phenolic diterpenes Totarol 5 and Sempervirol 6 respectively (Scheme 1). These compounds were originally isolated from the wood of Tetraclinis articulata and from the resin of Cupressus sempervirens respectively. Recently Totarol 5 has also been discovered in the Chilean Podocarpaceae, juniperus and Mediterranean propolis. It has been approved for use as an antimicrobial additive in toothpaste and acne treatments and for prophylaxis of schistosomiasis and fascioliasis in humans, sheep, goats and cattle. The antibacterial activity of Totarol 5 and anthelmintic activity of Sempervirol 6 are well documented. In the event, to a mixture of commercially available PPA and 2-PrOH heated to 75–80 C we added the tetralone 1 and the mixture was heated for 5 h to obtain a viscous material. This contained a mixture of recovered tetralone 1 and three products of different intensities (but distinct Rf values) as evidenced in thin layer chromatography. Chromatographic purification afforded tetralones 2, 3 and 4 in yields of 10%, 20% and 32% respectively (Scheme 1). The structures of the tetralones 2, 3 and 4 were ascertained by H NMR and C NMR spectroscopy (see Experimental Section). When the isopropylation experiment was carried out by heating the reaction mixture at 100–110 C for 10h, the tetralone 4
2014 11th International Conference on Electrical Engineering, Computing Science and Automatic Control (CCE), 2014
Transparent and conductive Indium-doped zinc oxide (ZnO:In) thin films were deposited on glass su... more Transparent and conductive Indium-doped zinc oxide (ZnO:In) thin films were deposited on glass substrates by the ultrasonic spray pyrolysis technique. ZnO:In thin films were prepared by mixing 0.2M zinc acetate and 0.2M indium sulphate dissolved in a mixture of water, acetic acid and methanol. Indium sulphate which acts as the In source was chosen at three different atomic concentrations, namely, 1, 2, and 3 at. % and the films were deposited at a temperature ranging between 385 °C and 430 °C. The dependence of the electrical and optical properties on the substrate temperature and the dopant concentration was studied. Electrical resistivity as low as 1.6×10-3 Ωcm, electron mobility around 11 cm2/(V-s), carrier concentration in the range 4.96-8.98 ×1020 cm-3, and an optical transmittance of about 80 % was achieved for 3 at. % ZnO:In thin films.
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Papers by 104 Alexis Adrián Castillo Maldonado