Search results for "cascade reaction"

Step growth polymerization via tandem ene and diels-alder reactions

1997

In contrast to other electron deficient enophiles or dienophiles which react with 1,4-cyclohexadiene (1,4-CHD) under aromatization, 1,2,4-triazoline-3,5-diones react in a defined reaction sequence. In a first step the 1,4-cyclohexadiene reacts via an ene-reaction. The intermediately formed substituted 1,3-cyclohexadiene immediately reacts in a Diels-Alder reaction. The regiochemistry of the Diels-Alder reaction is controlled by the solvent polarity. This reaction sequence can be used to synthesize polymers. Low-molar-mass model compounds were synthesized to elucidate the stereochemistry of the polymers. By varying the bistriazolinedione, polymers with backbones of different rigidity are ava…

Synthesis of Polycyclic Indolines by Utilizing a Reduction/Cyclization Cascade Reaction

2021

European journal of organic chemistry 2021(45), 6097-6101 (2021). doi:10.1002/ejoc.202101191

Cover Feature: Synthesis of Polycyclic Indolines by Utilizing a Reduction/Cyclization Cascade Reaction (Eur. J. Org. Chem. 45/2021)

2021

Lewis Acid Mediated Domino Reaction between 2-Cyclohexenone and Methyl Azide - A DFT Study

2005

We have studied the Lewis acid mediated domino reaction between 2-cyclohexenone and methyl azide at the B3LYP/6-31G* and B3LYP/6-31+G**//B3LYP/6-31G* levels of theory. A complete survey of the potential energy surface is presented, and the structures of the stationary points and the corresponding molecular mechanism are discussed. The calculations suggest that the product, a cyclopentanone derivative, is formed by means of a domino process that comprises three consecutive reactions. The first and rate-limiting step is a concerted 1,3-dipolar cycloaddition between the Lewis acid coordinated cyclohexenone and methyl azide that yields the corresponding bicyclic 1,2,3-triazoline. The second rea…

Perfluoroketene dithioacetals and perfluorodithiocarboxylic acid derivatives: Versatile tools for organofluorine synthesis

2007

Perfluoroketene dithioacetals are simple and versatile compounds that can be transformed into a large variety of trifluoromethyl derivatives, in particular aza- and thiaheterocycles, perhalodithiocrotonic esters, and fluorinated dithiol thiones. These unsaturated perfluorodithioesters and analogs give interesting polar cycloaddition reactions whose mechanism is strongly influenced by the fluorine substitution. This substitution plays an important role in the reactivity of saturated perfluorodithiocarboxylic acids as well. Except for the carbophilic addition of allyl Grignard reagents to perfluorocarboxamides, a domino thiophilic addition-fluoride elimination was the main reaction process. I…

Unveiling the high reactivity of benzyne in the formal [3+2] cycloaddition reactions towards thioamides through the Molecular Electron Density Theory

2020

Abstract The domino reaction of benzyne with thioamide has been studied within the Molecular Electron Density Theory (MEDT) at the MPWB1K/6-311G(d) level. This domino reaction takes place through i) a formal [3 + 2] cycloaddition (32CA) reaction affording an ammonium ylide, and ii) an extrusion of ethylene from this species yielding a dihydrothiazole. Topological analysis of the electron density of benzyne shows its pseudodiradical structure, that is, without any energy cost, changes to a carbenoid one, allowing its participation as electrophile in polar reactions. As a consequence, the formal 32CA reaction does not have an activation enthalpy. Analysis of the changes of electron density al…

Asymmetric Synthesis of Functionalized Tricyclic Chromanes via an Organocatalytic Triple Domino Reaction

2017

A highly stereoselective triple domino reaction for the synthesis of functionalized tricyclic chromane scaffolds has been developed. A secondary amine-catalyzed domino Michael/Michael/aldol condensation reaction between aliphatic aldehydes, nitro-chromenes, and α,β-unsaturated aldehydes leads to the formation of synthetically important tricyclic chromanes bearing four contiguous stereogenic centers including a tetrasubstituted carbon in good yields (20–66%) and excellent stereoselectivities (>20:1 dr and >99% ee).

Asymmetric Tandem Reactions: New Strategies and Applications

2013

Abstract The application of allylic sulphoxides and, particularly, the chiral amine reagent tert-butanesulphinamide has been extended to three different tandem processes. The condensation of (R)-(+)-allyl p-tolyl sulphoxide, fluorinated nitriles and alkyl propiolates led to a new family of enantiomerically pure fluorine-containing 1,4- dihydropyridines. A diastereoselective nucleophilic addition of fluorinated nucleophiles onto (R)-(tert-butanesulphinyl) imines, followed by an intramolecular aza-Michael reaction gave rise to either fluorinated isoindolines or 3-substituted indanones in a stereoselective manner.

Dienediolates of unsaturated carboxylic acids in synthesis. Synthesis of cyclohexenones and polycyclic ketones by tandem Michael-Dieckmann decarboxyl…

1994

Abstract Substituted 2-cyclohexenones 4 to 7 and hexaxydronaphthalenones and hexahydroindenones 13 to 18 are prepared by tandem Michael-Dieckmann addition of lithium dienediolates of acyclic and alicyclic unsaturated carboxylic acids to the lithium salts of the same or other unsaturated carboxylic acids.

Fluorogenic Enzyme-Triggered Domino Reactions Producing Quinoxalin-2(1H)-one-based Heterocycles

2020

International audience; A simple and effective biocompatible domino reaction triggered by a model protease and leading to formation of strongly fluorescent quinoxalin-2(1H)-one N-heterocycles is described. Some positive attributes including versatility and ability to provide outstanding fluorescence "OFF-ON" responses were revealed by this work. They open the way for practical applications of this novel type of "covalent-assembly" based fluorescent probes in the fields of sensing and bioimaging. Among the myriad of synthetic transformations and catalysts currently available for concise and efficient synthesis of organic molecules, bioinspired approaches based on the use of enzymes often int…