Person: Moreno Jiménez, Florencio
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First Name
Florencio
Last Name
Moreno Jiménez
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Óptica y Optometría
Department
Química Orgánica
Area
Química Orgánica
Identifiers
6 results
Search Results
Now showing 1 - 6 of 6
Item The Mechanism of Hydrolysis of Aryldiazonium Ions Revisited: Marcus Theory vs. Canonical Variational Transition State Theory(European Journal of Organic Chemistry, 2013) García Martínez, Antonio; Moya Cerero, Santiago de la; Osío Barcina, José de Jesús; Moreno Jiménez, Florencio; Lora Maroto, BeatrizSeveral models, theoretical levels and computational methods, all based on the canonical variational transition state approximation, have been used to predict both the experimental activation energies (ΔEexp≠) and the experimental activation free energies (ΔGexp≠) for the hydrolysis of aryldiazonium ions. It is demonstrated that the computation of activation energies (ΔE≠), instead of activation free energies (ΔG≠), agrees better with the corresponding experimental data, showing that the employed computational methods do not afford reliable entropic contributions to the free energy barriers in the case of the studied reaction. However, the most fitted computations of ΔE≠ were not able to clearly differentiate between the mechanisms proposed for this interesting reaction (SN1, SN2 and water cluster). In contrast, the use of the Marcus theory (hyperbolic-cosine equation) instead of the canonical variational transition state theory leads to excellent agreement between the in-water-computed activation energies (ΔEwM≠) and the corresponding ΔEexp≠ values for the SN2 mechanism, but far beyond the limit of error for the SN1 process. The validity of the Marcus theory for the studied SN1 and SN2 reactions is ensured by the fact that both reactions can be described as SET processes. On the other hand, apparently compelling evidence against the SN2 mechanism, such as 13C KIEs and experimental observation of N2 scrambling, are also discussed and alternative explanations are proposed.Item Photochemical Oxidation of Thioketones by Singlet Molecular Oxygen Revisited: Insights into Photoproducts, Kinetics, and Reaction Mechanism(Journal of organic chemistry, 2015) Sánchez Arroyo, Antonio José; Pardo Botero, Zulay D.; Moreno Jiménez, Florencio; Herrera Fernández, Antonio; Martín, Nazario; García Fresnadillo, DavidPhotosensitized oxidation of trimethyl[2.2.1]-bicycloheptane thioketones by 1 O2 can yield more photoproducts than exclusively ketones and sulfines. Moreover, the ketone/sulfine ratio can be reversed when protic conditions and high thioketone concentrations are used, conversely to earlier results reporting ketones as the main photoproducts. A new mechanistic proposal for sulfine formation is suggested following intermolecular oxygen transfer from a peroxythiocarbonyl intermediate to a second thioketone molecule. Reaction quantum yields (10−5−10−2) depend on the reaction conditions and time. Sulfine production reaches a maximum at short irradiation times, whereas decomposition to the corresponding ketone is observed at long reaction times. When the thioketone substrate has a hydrogen atom at the α position a peroxyvinylsulfenic acid intermediate can be formed by proton transfer. Reaction of this intermediate with another thioketone molecule can yield more sulfine and its tautomeric vinylsulfenic acid, which dimerizes in situ to the thiosulfinate. The hydroperoxyl group of the peroxyvinylsulfenic acid can also rearrange to the α position, and by reaction with the starting thioketone, α-hydroxy thioketone and additional sulfine can be formed, while dehydration yields the α-oxo thioketone. In situ [2 + 2] and [4 + 2] self-cycloaddition of the α-oxo thioketone yields significant amounts of the corresponding adducts at prolonged irradiation times.Item A short and convenient procedure for the stereoselective synthesis of 2-hydroxy-1-norbornanesulfonamides(Tetrahedron: Asymmetry, 2004) Garcı́a Martı́nez, Antonio; Teso Vilar, Enrique; Moreno Jiménez, Florencio; Álvarez Garcı́a, Ana MªA short and convenient procedure for the stereoselective synthesis of novel optically active 2-hydroxy-1-norbornanesulfonamides starting from commercially available natural camphor and fenchone is reported. The synthetic route involves a nucleophilic substitution at the sulfenyl sulfur atom of 2-methylene-1-norbornylthiotriflates followed by oxidation of the intermediate sulfenamides and highly diastereoselective reduction of the carbonyl group of the parent 2-oxo-1-norbornanesulfonamides.Item A novel and simple procedure for the enantiospecific synthesis of bridgehead norbornane thioethers and thiocyanates(Tetrahedron: Asymmetry, 2002) Garcı́a Martı́nez, Antonio; Teso Vilar, Enrique; Moreno Jiménez, Florencio; Álvarez García, Ana María; Pinilla Rodríguez, PatriciaAn easy three-step route for the enantiospecific synthesis of novel 1-norbornyl thioethers and thiocyanates from readily available natural fenchone and camphor is described. The key step of the synthetic route is the nucleophilic substitution over the sulfenyl sulfur atom of the intermediate thiotriflates by the corresponding C-nucleophiles.Item New procedures for the synthesis of heterocyclic substituted and 2,4-difunctionalized pyrimidines(Tetrahedron, 1996) García Martínez, Antonio; Herrera Fernández, Antonio; Moreno Jiménez, Florencio; Muñoz Martínez, Pablo J.; Alonso Martín, Cristina; Subramanian, Laksminarayanapuran R.N-Tosyl-2- and -3-acetylpyrrols 1 or N-tosyl-2-pyrrolidone 5 were condensed with cyano compounds in the presence of triflic anhydride (Tf2O) to yield heteroarylpyrimidines. 2,4 Difunctionalized pyrimidines were obtained by reaction of the corresponding 2,4-bis(methylsulfonyl)pyrimidines with nucleophiles.Item Enantiospecific synthesis of substituted 1-norbornanesulfonic acids and 1-norbornanesulfenic and sulfonic acid derivatives(Tetrahedron: Asymmetry, 2000) Garcı́a Martı́nez, Antonio; Teso Vilar, Enrique; Moreno Jiménez, Florencio; Garcı́a Amo, MaríaNew homochiral 1-norbornanesulfenic and sulfonic acid derivatives 2–7, as well as the sulfonic acids 8, are easily synthesised starting from 2-methylene-1-norbornylthiotriflates 1. This new class of homochiral bridgehead thiosulfonates was prepared by us from naturally occurring (+)-camphor and (−)-fenchone. Nucleophilic substitution at the sulfenyl sulfur atom is the key step for this synthetic strategy