Search results for "Cascade reaction"
showing 10 items of 52 documents
Thiourea-Catalyzed Domino Michael–Mannich [3+2] Cycloadditions: A Strategy for the Asymmetric Synthesis of 3,3′-Pyrrolidinyl-dispirooxindoles
2017
The asymmetric synthesis of trifluoromethylated 3,3′-pyrrolidinyl-dispirooxindole derivatives with four contiguous stereogenic centers, including two vicinal spiro-stereocenters, is described. Employing a bifunctional thiourea catalyst, a domino Michael–Mannich [3+2] cycloaddition occurs readily between isatin ketimines and isatin-derived enoates with good yields and very high stereoselectivities, providing a direct entry to the title compounds of potential medical value.
New Fluorinated Peptidomimetics through Tandem Aza-Michael Addition to α-Trifluoromethyl Acrylamide Acceptors: Synthesis and Conformational Study in …
2009
A range of partially modified retro (PMR) psi[NHCH(2)] peptide mimetics containing a hydrolytically stable CH(2)CH(CF(3))CO unit have been synthesized. The first kind of peptidomimetics is obtained from the highly efficient aza-Michael addition of different amines to alpha-trifluoromethyl acrylamide acceptors. Subsequent deprotection of the amino group furnishes the key common intermediate for the synthesis of other families of peptidomimetics: dipeptides, tripeptides, peptidomimetics containing a urea moiety, and structures containing two units of alpha-trifluoromethyl-beta(2)-alanine. Finally, a conformational study of several of the newly synthesized peptidomimetics, performed with the a…
Asymmetric Organocatalytic Michael Addition–Cyclization Cascade of Cyclopentane-1,2-dione with Substituted α,β-Unsaturated Aldehydes
2017
An asymmetric organocatalytic Michael addition–cyclization cascade reaction has been developed using cyclopentane-1,2-dione as a Michael donor and α,β-unsaturated aldehydes as Michael acceptors. Bicyclic hemiacetals were obtained in excellent yields and enantioselectivities. On the basis of the results, a one-pot reaction has been developed to obtain chiral 3-substituted cyclopentane-1,2-diones and substituted dihydropyrans in good yields and excellent enantioselectivity.
ChemInform Abstract: Gold Catalyzed Stereoselective Tandem Hydroamination-Formal Aza-Diels-Alder Reaction of Propargylic Amino Esters.
2013
The overall sequence of the tandem reaction presented here leads to nitrogen-containing tetracycles under formation of 4 bonds and five stereocenters, in most cases as single diastereoisomers.
Gold-Catalyzed Tandem Hydroamination/Formal Aza-Diels-Alder Reaction of Homopropargyl Amino Esters: A Combined Computational and Experimental Mechani…
2015
A tandem gold-catalyzed hydroamination/formal aza-Diels-Alder reaction is described. This process, which employs quaternary homopropargyl amino ester substrates, leads to the formation of an intrincate tetracyclic framework and involves the generation of four bonds and five stereocenters in a highly diastereoselective manner. Theoretical calculations have allowed us to propose a suitable mechanistic rationalization for the tandem protocol. Additionally, by studying the influence of the ligands on the rate of the gold-catalyzed reactions, it was possible to establish optimum conditions in which to perform the process with a variety of substituents on the amino ester substrates. Notably, the …
Friedel-Crafts Alkylation of Arenes in Total Synthesis
2015
Conversion of levulinic acid to γ-valerolactone over Zr-containing metal-organic frameworks: Evidencing the role of Lewis and Brønsted acid sites
2021
Zr-containing UiO-66 and MOF-808 are evaluated for converting levulinic acid (LA) into γ-valerolactone (GVL) through various routes: (i) Step-wise esterification of LA to n-butyl levulinate (nBuL) and Meerwein-Ponndorf-Verley (MPV) reduction to GVL; (ii) One-pot two-steps esterification with n-butanol followed by MPV reduction with sec-butanol; and (iii) direct conversion of LA into GVL through a tandem reaction. Selection of this multistep complex reaction evidences the participation of the different acid sites (Lewis or Brønsted) of the material in each individual step: Brønsted-induced acid sites catalyze esterification reaction efficiently, while Lewis acid sites are the preferred sites…
The domino reaction between 4,6-dinitrobenzofuroxan and cyclopentadiene. Insights on the nature of the molecular mechanism
2004
Abstract The molecular mechanism of the domino reaction between 4,6-dinitrobenzofuroxan, 1 , and cyclopentadiene, Cp, to give the adduct 11 is examined through density functional theory (DFT) calculations at B3LYP/6-31G* level. This domino reaction comprises two consecutive formally [4+2] cycloadditions. The first one is a two-center addition initialized by the nucleophilic attack of Cp to the more electrophilic center of 1 . The subsequent cyclization can take place along two competitive channels associated to the formation of a second C–C bond yielding the formally [2+4] cycloadduct 9 , or a C–O bond yielding the formally [4+2] cycloadduct 10 . The second cycloaddition is a stepwise proce…
ChemInform Abstract: Asymmetric Synthesis of Cyclopentanes Bearing Four Contiguous Stereocenters via an NHC-Catalyzed Michael/Michael/Esterification …
2016
An NHC-catalyzed Michael/Michael/esterification domino reaction via homoenolate/enolate intermediates for the asymmetric synthesis of tetrasubstituted cyclopentanes bearing four contiguous stereocenters is described. A variety of α,β-unsaturated aldehydes and 2-nitroallylic acetates react well with good domino yields and high stereoselectivities.
Asymmetric synthesis of cyclopentanes bearing four contiguous stereocenters via an NHC-catalyzed Michael/Michael/esterification domino reaction.
2016
An NHC-catalyzed Michael/Michael/esterification domino reaction via homoenolate/enolate intermediates for the asymmetric synthesis of tetrasubstituted cyclopentanes is described.