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290 results on '"Oltra, J. Enrique"'

1. Unexpected TiIII/Mn-Promoted Pinacol Coupling of Ketones

Author

Paradas, Miguel, Campaña, Araceli G., Estévez, Rosa E., Álvarez de Cienfuegos, Luis, Jiménez, Tania, Robles, Rafael, Cuerva, Juan M., and Oltra, J. Enrique

Abstract

Titanocene(III) chemistry has emerged in the last decades as an indispensable tool in C−C bond-forming reactions. In this context, pinacol and related reactions allow the stereoselective synthesis of vicinal diols. In this work, we present new applications of these reactions using as starting materials aromatic ketones. Simple and smooth reaction conditions have been developed and have been applied for inter- and intramolecular processes. We also describe that although Cp2TiCl is usually used as a monoelectronic reducing agent, it can be also used as an efficient Lewis acid.

Published
2024
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10. General approach to polycyclic meroterpenoids based on Stille couplings and titanocene catalysts

Author

Justicia, Jose, Oltra, J. Enrique, Cuerva, Juan M., and Yaru Shi

Subjects
Olefins -- Research, Biological sciences, Chemistry
Abstract

A novel convergent procedure that has proved useful in the synthesis of a wide range of meroterpenoid-related structures containing a mono-, sesqui, or diterpenoid moiety linked to a nonfused aromatic subunit with various substitution patterns is discussed. The coupling reaction is perfectly compatible with preformed epoxides, while the sequential cyclixation provide exocyclic alkenes.

Published
2004

11. Hydrogen Atom Donors: Recent Developments

Author

Gansäuer, Andreas, primary, Shi, Lei, additional, Otte, Matthias, additional, Huth, Inga, additional, Rosales, Antonio, additional, Sancho-Sanz, Iris, additional, Padial, Natalia M., additional, and Oltra, J. Enrique, additional

Published
2011
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13. Synthesis of (+)-8-deoxyvernolepin and its 11,13-dihydroderivative. A novel reaction initiated by sulfene elimination leads to the 2-oxa-cis-decalin skeleton

Author

Barrero, Alejandro F., Oltra, J. Enrique, Alvarez, Miriam, and Rosales, Antonio

Subjects
Chemistry, Organic -- Research, Enantiomers -- Physiological aspects, Hydrogen -- Physiological aspects, Chemical reactions -- Analysis, Biological sciences, Chemistry
Abstract

Research has been conducted on the (+)-8-deoxyvernolepin and its 11,13-dihydroderivative. The enantioselective synthesis of these compounds has been carried out and the results indicate that the employed synthetic strategy is useful for the enantioselective preparation of (+)-vernolepin-related compounds from germacrolides.

Published
2002

14. Effects of solvents and water in Ti(III)-mediated radical cyclizations of epoxygermacrolides. Straightforward synthesis and absolute stereochemistry of (+)-3alpha-hydroxyreynosin and related eudesmanolides

Author

Barrero, Alejandro F., Oltra, J. Enrique, Cuerva, Juan M., and Rosales, Antonio

Subjects
Chemistry, Organic -- Research, Ring formation (Chemistry) -- Physiological aspects, Titanium -- Physiological aspects, Water -- Physiological aspects, Solvents -- Physiological aspects, Macrolide antibiotics -- Physiological aspects, Epoxy compounds -- Physiological aspects, Biological sciences, Chemistry
Abstract

Research has been conducted on eudesmanolides which are the sequiterpene lactones' main skeletal types. The results of the straightforward synthesis of such eudesmanolides as (+)-3alpha-hydroxyreynosin and (+)-8beta-hydroxyasterolide carried out via different solvents and additives and containing exocyclic double bond are reported.

Published
2002

16. Asymmetric Reduction of Ketones

Author

Dubrovina, Natalia, primary, Börner, Armin, additional, Nakamura, Kaoru, additional, Fujii, Mikio, additional, Ida, Yoshiteru, additional, Rosales, Antonio, additional, Cuerva, Juan M., additional, Oltra, J. Enrique, additional, Moran, Paul H., additional, Henschke, Julian P., additional, Zanotti-Gerosa, Antonio, additional, Lennon, Ian C., additional, Stephan, Michel Massoud S., additional, Mohar, Barbara, additional, Wills, Martin, additional, Xu, Yingjian, additional, Docherty, Gorden, additional, Woodward, Gary, additional, Wettergren, Jenny, additional, Adolfsson, Hans, additional, Jeulin, Séverine, additional, Ratovelomanana-Vidal, Virginie, additional, Genet, Jean-Pierre, additional, Burri, Estelle, additional, Wendicke, Silke B., additional, Severin, Kay, additional, Guo, Minjie, additional, Li, Dao, additional, Sun, Yanhui, additional, Zhang, Zhaoguo, additional, Chai, Liting, additional, Li, Yangzhou, additional, Wang, Quanrui, additional, Wang, Guangyin, additional, and Zhao, Gang, additional

Published
2007
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19. CpTiCl2‐Catalyzed Cross‐Coupling between Internal Alkynes and Ketones: A Novel Concept in the Synthesis of Halogenated, Conjugated Dienes.

Author

Roldan‐Molina, Esther, Nievas, Maria M., Navarro, Jorge A. R., and Oltra, J. Enrique

Subjects
KETONES, DIOLEFINS, ALKYNES, SONOGASHIRA reaction, NATURAL products
Abstract

A novel concept for the synthesis of halogenated, conjugated dienes is disclosed: the CpTiCl2‐catalyzed coupling of keto‐alkynes, in the presence of Me3SiBr/Et3N⋅HBr. This reaction provided five‐, six‐, and seven‐membered carbocycles, nitrogenated heterocycles, as well as six‐membered oxygenated heterocycles leading to a brominated conjugate diene. These products showed high reactivity in the Diels–Alder, Suzuki, and Sonogashira reactions, giving complex chemical structures in only three steps from the corresponding acyclic keto‐alkyne. Hopefully, this strategy will pave the way towards the synthesis of bioactive natural products and new materials. [ABSTRACT FROM AUTHOR]

Published
2020
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21. Mn(0)-mediated chemoselective reduction of aldehydes: application to the synthesis of [alpha]-deuterioalcohols

Author

Jimenez, Tania, Barea, Elisa, Oltra, J. Enrique, Cuerva, Juan M., and Justicia, Jose

Subjects
Alcohols -- Chemical properties, Aldehydes -- Chemical properties, Deuterium -- Chemical properties, Manganese -- Chemical properties, Oxidation-reduction reaction -- Analysis, Biological sciences, Chemistry
Abstract

A mild, simple, safe, chemoselective reduction of different kinds of aldehydes to the corresponding alcohols mediated by the Mn dust/water system is described. An efficient, inexpensive alternative for the preparation of the same type of compounds through the synthesis of [alpha]-deuterated alcohols in presence of [D.sub.2]O is also described.

Published
2010

22. Understanding the exceptional hydrogen-atom donor characteristics of water in [Ti.sup.III]-mediated free-radical chemistry

Author

Paradas, Miguel, Campana, Araceli G., Jimenez, Tania, Robles, Rafael, Oltra, J. Enrique, Bunuel, Elena, Justicia, Jose, Cardenas, Diego J., and Cuerva, Juan M.

Subjects
Hydrogen -- Atomic properties, Hydrogen -- Chemical properties, Organometallic compounds -- Structure, Organometallic compounds -- Chemical properties, Titanium -- Chemical properties, Chemistry
Abstract

A study was conducted to demonstrate the efficiency of titanocene(III) aqua complexes as a unique class of hydrogen-atom donor (HAT) reagents based on two key features such as excellent binding capabilities of water toward titanocene(III) complexes and a low activation energy for the HAT step. The results provide insight into the remarkable hydrogen-atom donor characteristics of water in [Ti.sup.III]-mediated free-radical chemistry.

Published
2010

23. Unexpected [Ti.sup.III]/Mn-promoted pinacol coupling of ketones

Author

Paradas, Miguel, Campana, Araceli G., Estevez, Rosa E., de Cienfuegos, Luis Alvarez, Jimenez, Tania, Robles, Rafael, Cuerva, Juan M., and Oltra, J. Enrique

Subjects
Aromatic compounds -- Chemical properties, Aromatic compounds -- Structure, Lewis structures -- Analysis, Titanium compounds -- Chemical properties, Titanium compounds -- Structure, Biological sciences, Chemistry
Abstract

Titanocene(III) chemistry is used as indispensible tool in C-C bond-forming reactions and pinacol and related reactions have allowed the steresoselective synthesis of vicinal diols. Smooth reaction conditions are applied for inter- and intramolecular processes and [Cp.sub.2]TiCl is also used as an efficient Lewis acid.

Published
2009

24. Ti-Catalyzed Reformatsky-type coupling between [alpha]-halo ketones and aldehydes

Author

Estevez, Rosa E., Paradas, Miguel, Millan, Alba, Jimenez, Tania, Robles, Rafael, Cuerva, Juan M., and Oltra, J. Enrique

Subjects
Titanium compounds -- Structure, Titanium compounds -- Chemical properties, Spin coupling -- Research, Ketones -- Chemical properties, Catalysis -- Analysis, Biological sciences, Chemistry
Abstract

The first Ti-catalyzed Reformatsky-type coupling between [alpha]-halo ketones and aldehydes is described. This reaction has afforded [beta]-hydroxy ketones and the catalytic cycle has proceeded via bis(cyclopentadienyl)titanium enolates.

Published
2008

25. 7-endo radical cyclizations catalyzed by titanocene(III). Straightforward synthesis of terpenoids with seven-membered carbocycles

Author

Justicia, Jose, Oller-Lopez, Juan L., Campana, Araceli G., Oltra, J. Enrique, Cardenas, Diego J., Cuerva, Juan M., and Bunuel, Elena

Subjects
Ring formation (Chemistry) -- Analysis, Carbocyclic compounds -- Structure, Carbocyclic compounds -- Chemical properties, Chemistry
Abstract

A novel procedure for the straightforward synthesis of seven-membered carbocycles through free-radical chemistry, based on titanocene(III)-catalyzed 7-endo-dig and 7-endo-trig cyclizations is described. This procedure is proved to be useful for the preparation of several natural products including mono-, sesqui-, and diterpenoids with different skeletons containing cycloheptane rings.

Published
2005

26. Exploiting Pd(super II) and T(super III) chemistry to obtain gamma-dioxygenated terpenoids: Synthesis of rostratone and novel approaches to aphidicolin and pyripyropene A

Author

Justicia, Jose, Oltra, J. Enrique, and Cuerva, Juan M.

Subjects
Palladium -- Structure, Palladium -- Chemical properties, Chemical synthesis -- Analysis, Biological sciences, Chemistry
Abstract

A novel strategy for the synthesis of terpenoids with a characteristic gamma-dioxygenated system on the A ring is developed involving three stages. This strategy has proved to be useful for the synthesis of the natural labdane rostratone and related terpenoids, as well as for advanced synthetic approaches toward the pharmacologically active products aphidicolin and pyripyropene A.

Published
2005

28. Chemical Warfare Agents Detoxification Properties of Zirconium Metal–Organic Frameworks by Synergistic Incorporation of Nucleophilic and Basic Sites

Author

Gil-San-Millan, Rodrigo, primary, López-Maya, Elena, additional, Hall, Morgan, additional, Padial, Natalia M., additional, Peterson, Gregory W., additional, DeCoste, Jared B., additional, Rodríguez-Albelo, L. Marleny, additional, Oltra, J. Enrique, additional, Barea, Elisa, additional, and Navarro, Jorge A. R., additional

Published
2017
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29. Cp2TiCl: An Ideal Reagent for Green Chemistry?

Author

Castro Rodríguez, María, primary, Rodríguez García, Ignacio, additional, Rodríguez Maecker, Roman Nicolay, additional, Pozo Morales, Laura, additional, Oltra, J. Enrique, additional, and Rosales Martínez, Antonio, additional

Published
2017
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30. Ti-Catalyzed Synthesis of Exocyclic Allenes on Oxygen Heterocycles

Author

Padial, Natalia M., primary, Hernández-Cervantes, Carmen, additional, Muñoz-Bascón, Juan, additional, Roldán-Molina, Esther, additional, García-Martínez, Mireya, additional, Ruiz-Muelle, Ana Belén, additional, Rosales, Antonio, additional, Álvarez-Corral, Míriam, additional, Muñoz-Dorado, Manuel, additional, Rodríguez-García, Ignacio, additional, and Oltra, J. Enrique, additional

Published
2017
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32. CpTiCl2, an Improved Titanocene(III) Catalyst in Organic Synthesis.

Author

Roldan‐Molina, Esther, Padial, Natalia M., Lezama, Luis, and Oltra, J. Enrique

Subjects
CATALYSTS, LIGANDS (Chemistry), KETONES, CHARGE exchange, ALLYLATION
Abstract

Preparation, EPR analysis, and advantages in green organic chemistry of CpTiCl2, an improved single‐electron transfer catalyst, are reported. Under mild conditions, this organometallic complex provides excellent yields of homoallylic and homopropargylic alcohols in Barbier‐type allylation and propargylation reactions. Moreover, in the presence of a bidentate BOX ligand, Barbier‐type cyclization reactions catalyzed by CpTiCl2 can be carried out in an enantioselective manner. CpTiCl2, an improved titanocene(III) single‐electron transfer catalyst, under mild conditions provides excellent yields of homoallylic and homopropargylic alcohols in Barbier‐type allylation and propargylation reactions. Moreover, in the presence of a BOX ligand, it was capable of catalyzing enantioselective intramolecular allylations and propargylations (cyclizations) of ketones. [ABSTRACT FROM AUTHOR]

Published
2018
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37. Synthesis of (±)-Aureol by Bioinspired Rearrangements

Author

Rosales, Antonio, primary, Muñoz-Bascón, Juan, additional, Roldan-Molina, Esther, additional, Rivas-Bascón, Nazaret, additional, Padial, Natalia M., additional, Rodríguez-Maecker, Roman, additional, Rodríguez-García, Ignacio, additional, and Oltra, J. Enrique, additional

Published
2015
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38. Aproximación a la síntesis enantioselectiva de achillifolina.

Author

Rosales Martínez, Antonio, Muñoz Bascón, Juan, Castilla Alcalá, José Antonio, Roldán Molina, Esther, Olmedo, Santiago, Proaño, Janeth, Oltra, J Enrique, Rosales Martínez, Antonio, Muñoz Bascón, Juan, Castilla Alcalá, José Antonio, Roldán Molina, Esther, Olmedo, Santiago, Proaño, Janeth, and Oltra, J Enrique

Abstract

In this paper, an approximation biomimetic synthesis of achillifoline, a natural sesquiterpene lactone isolated from Achillea millefolium subsp. Millenium, is presented. Carbocationic cyclization of epoxy-costunolide is the key step of the synthetic sequence. This transannular cyclization, allows the formation of the skeleton of 1,4-epoxy-cyclodecane presents in achillifoline, En este artículo se presenta una aproximación biomimética a la síntesis enantioselectiva de achillifolina, una lactona sesquiterpénica natural aislada de Achillea millefolium subsp. Millenium. La ciclación carbocatiónica de epoxi-costunolida es la etapa clave de la secuencia sintética. Esta ciclación transanular permite la formación del esqueleto de 1,4-epoxi-ciclodecano presente en (+)-achillifolina

Published
2014

44. Highly Hydrophobic Isoreticular Porous Metal–Organic Frameworks for the Capture of Harmful Volatile Organic Compounds

Author

Padial, Natalia M., primary, Quartapelle Procopio, Elsa, additional, Montoro, Carmen, additional, López, Elena, additional, Oltra, J. Enrique, additional, Colombo, Valentina, additional, Maspero, Angelo, additional, Masciocchi, Norberto, additional, Galli, Simona, additional, Senkovska, Irena, additional, Kaskel, Stefan, additional, Barea, Elisa, additional, and Navarro, Jorge A. R., additional

Published
2013
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48. Diastereoselective Synthesis of (±)-Ambrox by Titanium(III)-Catalyzed Radical Tandem Cyclization.

Author

Rosales, Antonio, Foley, L. A. R., Padial, Natalia M., Muñoz-Bascón, Juan, Sancho-Sanz, Iris, Roldan-Molina, Esther, Pozo-Morales, Laura, Irías-Álvarez, Adriana, Rodríguez-Maecker, Roman, Rodríguez-García, Ignacio, and Oltra, J. Enrique

Subjects
AMBERGRIS, RING formation (Chemistry), STEREOSELECTIVE reactions, CHEMICAL radical synthesis, FARNESOL
Abstract

A synthesis of (±)-ambrox, a compound with delicious am bergris-type scent, is presented. The key step is a highly diastereoselective titanocene(III)-catalyzed radical tandem cyclization of a farneso derivative. [ABSTRACT FROM AUTHOR]

Published
2016
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