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19 results on '"Parella, Teodor"'

6. Chiral Induction in Intramolecular Rhodium-Catalyzed [2+2+2] Cycloadditions of Optically Active Allene-ene/yne-allene Substrates.

Author

Haraburda, Ewelina, Fernández, Martí, Gifreu, Anna, Garcia, Jordi, Parella, Teodor, Pla ‐ Quintana, Anna, and Roglans, Anna

Subjects
ASYMMETRIC synthesis, PLATINUM group, ALLENE synthesis, RING formation (Chemistry), RHODIUM catalysts
Abstract

Allene-yne-allene and allene-ene-allene N-tosyl-linked substrates with two chiral centres in the α-position of the allene moiety were satisfactorily prepared starting both from racemic and chiral propargylic alcohols. The Wilkinson's complex-catalyzed [2+2+2] cycloaddition reaction of these substrates was evaluated. In the case of enantiomerically pure bisallenes, high stereoselectivity was observed, giving a diastereomerically pure cycloadduct. The chirality of starting bisallene substrates can be completely transferred to the cycloadducts, representing an atom-economical and enantiospecific process for the construction of fused polycycles. However, when reacting an oxygen-linked allene-ene-allene substrate, the stereoselectivity decreased and two diastereoisomers were formed. A detailed characterization study of the resulting cycloadducts allowed us to identify the enantioisomer generated in the cycloaddition. [ABSTRACT FROM AUTHOR]

Published
2017
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17. Rhodium Nanoflowers Stabilized by a Nitrogen-Rich PEG-Tagged Substrate as Recyclable Catalyst for the Stereoselective Hydrosilylation of Internal Alkynes.

Author

Guo, Wusheng, Pleixats, Roser, Shafir, Alexandr, and Parella, Teodor

Subjects
RHODIUM catalysts, CATALYSTS recycling, HYDROSILYLATION, ALKYNE synthesis, ETHER (Anesthetic)
Abstract

Morphology and size controllable rhodium nanoparticles stabilized by a nitrogen-rich polyoxyethylenated derivative have been prepared by reduction of RhCl3 with NaBH4 in water at room temperature and fully characterized. The flower-like Rh NPs are effective and recyclable catalysts for the stereoselective hydrosilylation of challenging internal alkynes and diynes, affording the ( E)-vinylsilanes in quantitative yields for a wide range of substrates. The insolubility of the nanocatalyst in diethyl ether allows its easy separation and recycling. [ABSTRACT FROM AUTHOR]

Published
2015
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19. Functionalization of the 3-Position of Thiophene and Benzo[b]thiophene Moieties by Palladium-Catalyzed C—C Bond Forming Reactions using Diazonium Salts

Author

Raduán, Mónica, Padrosa, Joaquim, Pla‐Quintana, Anna, Parella, Teodor, and Roglans, Anna

Abstract

The palladium‐catalyzed Matsuda–Heck and Suzuki–Miyaura cross‐couplings of 2‐methoxycarbonylthiophene‐3‐diazonium tetrafluoroborate 1were performed to synthesize a series of thiophene derivatives functionalized in the β‐position. Good to excellent yields of the cross‐coupling products were obtained using palladium acetate [Pd(OAc)2], a ligandless palladium catalyst, without a base, at room temperature, under aerobic conditions and with short reaction times. A diazotization and cross‐coupling sequence can also be performed in a one‐pot process avoiding the isolation of the thiophenediazonium salt derivative. In addition, 2‐methoxycarbonylbenzo[b]thiophene‐3‐diazonium tetrafluoroborate 8was also efficiently arylated by applying the same Suzuki–Miyaura optimized reaction conditions.

Published
2011
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