Search results for "Pyrazolone"
showing 10 items of 14 documents
Regio- and Stereoselective Synthesis of 3-Pyrazolylidene-2-oxindole Compounds by Nucleophilic Vinylic Substitution of (E)-3-(Nitromethylene)indolin-2…
2019
[EN] A highly regio- and stereoselective synthesis of 3-alkylidene-2-oxindoles has been described through a nucleophilic vinylic substitution (SNV) of (E)-3-(nitromethylene)indolin-2-one using pyrazol-3-ones as nucleophiles and Et3N as a base. The reaction affords selectively the Z-isomer when pyrazol-3-ones without substituents at the 4 position are used. While the reaction is E-selective with 4- substituted pyrazolones. The stereoselectivity (up to >20:1) and the yields (up to 98%) are very high under mild reaction conditions.
Regio-, Diastereo-, and Enantioselective Organocatalytic Addition of 4-Substituted Pyrazolones to Isatin-Derived Nitroalkenes
2019
"This is the peer reviewed version of the following article: [FULL CITE], which has been published in final form at [Link to final article using the DOI]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."
Asymmetric, Three-Component, One-Pot Synthesis of Spiropyrazolones and 2,5-Chromenediones from Aldol Condensation/NHC-Catalyzed Annulation Reactions
2016
A novel one-pot, three-component diastereo- and enantioselective synthesis of spiropyrazolones has been developed involving the aldol condensation of an enal to generate α,β-unsaturated pyrazolones, which react with a second equivalent of enal through an N-heterocyclic carbene (NHC)-catalyzed [3+2] annulation. The desired spirocyclopentane pyrazolones are obtained in moderate to good yields and good to excellent stereoselectivities. Alternatively, starting from cyclic 1,3-diketones, 2,5-chromenediones are available through [2+4] annulation.
Recent Advances in Catalytic Enantioselective Synthesis of Pyrazolones with a Tetrasubstituted Stereogenic Center at the 4-Position
2020
AbstractPyrazolone [2,4-dihydro-3H-pyrazol-4-one] represents one of the most important five-membered nitrogen heterocycles which is present in numerous pharmaceutical drugs and molecules with biological activity. Recently, many catalytic methodologies for the asymmetric synthesis of chiral pyrazolones have been established with great success, specially, for the synthesis of pyrazolones bearing a tetrasubstituted stereocenter at C-4. This review summarizes these excellent research studies since 2018, including representative examples and some mechanistic pathways explaining the observed stereochemistry.1 Introduction2 Catalytic Enantioselective Synthesis of Chiral Pyrazolones with a Full Car…
Organocatalytic enantioselective aminoalkylation of pyrazol-3-ones with aldimines generated in situ from α-amido sulfones
2019
Herein, an efficient asymmetric aminoalkylation of pyrazolones with α-amido sulfones catalyzed by a quinine-derived squaramide in dichloromethane/aqueous media has been established. A variety of chiral amines were obtained with high yields (up to 98%) and excellent enantioselectivities (up to 99% ee). The corresponding products are transformed into optically active acetylated pyrazoles after treatment with Ac2O/Et3N, because of the instability of some adducts. The reaction tolerates a wide range of α-amido sulfones and different pyrazolones.
Organocatalytic Enantioselective Synthesis of Pyrazoles Bearing a Quaternary Stereocenter
2016
An efficient one-pot asymmetric synthesis of pyrazoles bearing a chiral quaternary stereocenter has been developed. Quinine-derived thiourea catalyzed the enantioselective addition of pyrazolones to isatin-derived ketimines, providing the corresponding acetylated pyrazoles after in situ treatment with Ac2O/Et3N. The corresponding pyrazoles were afforded in high yields and excellent enantioselectivities.
Asymmetric Synthesis of Amino-Bis-Pyrazolone Derivatives via an Organocatalytic Mannich Reaction.
2017
A new series of N-Boc ketimines derived from pyrazolin-5-ones have been used as electrophiles in asymmetric Mannich reactions with pyrazolones. The amino-bis-pyrazolone products are obtained in excellent yields and stereoselectivities by employing a very low loading of 1 mol % of a bifunctional squaramide organocatalyst. Depending on the substitution at position 4 of the pyrazolones, the new protocol allows for the generation of one or two tetrasubstituted stereocenters, including a one-pot version combing the Mannich reaction with a base-mediated halogenation. peerReviewed
Trichosporon beigelii pneumonia in a neutropenic patient.
1989
A case of pulmonary infection caused by Trichosporon beigelii is reported in an asthmatic patient undergoing steroid treatment who developed fever and lung infiltrates. Arthroconidia and blastoconidia were isolated from repeated sputum, bronchial aspirate and telescopic catheter samples. The infection coincided with neutropenia resulting from pyrazolone treatment. The response to amphotericin B treatment was favourable.
Organocatalytic Enantioselective Alkylation of Pyrazol-3-ones with Isatin-Derived Ketimines: Stereocontrolled Construction of Vicinal Tetrasubstitute…
2016
A quinine-derived thiourea catalysed the enantioselective addition of 4-substituted pyrazolones to isatin-derived ketimines, providing a variety of aminooxindole-pyrazolone adducts containing congested vicinal tetrasubstituted stereocentres with excellent outcomes (up to 98% yield, >20:1 dr and 98% ee).
Diastereoselective Synthesis of Spiro[pyrazolone-4,3′-tetrahydrothiophenes] via a Sulfa-Michael/Aldol Domino Reaction
2016
Synthesis : journal of synthetic organic chemistry 48(23), 4091-4098(2016). doi:10.1055/s-0035-1562473