Catalyzed Aza-Michael Addition Research Articles

Facile synthesis of 3-(pyrazol-1-yl) succinimides from Ag2CO3 -catalyzed aza-Michael addition of pyrazoles to maleimides

Herein, an effective and facile synthesis of 3-(pyrazol-1-yl) succinimides is first presented through silver-catalyzed aza-Michael addition of pyrazoles to maleimides. In the presence of 5 mol% of Ag2CO3, various pyrazoles smoothly reacted with maleimides in dichloroethane at 100 °C, to generate 3-(pyrazol-1-yl) succinimides in excellent yields. Notably, 3-substituted asymmetric pyrazoles exclusively give 3-pyrazolyl succinimides in excellent yields possibly due to the steric bulk of the 3-substituent excluding the formation of addition products of N 2. The method can also extend to gram scale.

β‐Aminosulfonyl Fluorides via Water‐Accelerated N‐Heterocyclic Carbene Catalysis

Herein, a water-accelerated, N-heterocyclic carbene (NHC)-catalyzed aza-Michael addition reaction was reported to access β-aminosulfonyl fluorides, which are key hubs of the sulfur(VI) fluoride exchange (SuFEx) reaction. As a crucial reaction medium, water considerably enhanced the reaction rate with excellent chemo- and site-selectivity (up to >99 : 1) compared to conventional solvents. In addition, the late-stage ligation of bioactive molecules with the aliphatic β-amino SuFEx hub was demonstrated. Mechanistic studies on experimental, analytical, and computational approaches support noncovalent activation over NHC catalysis "on-water".

Tuning Microenvironment of Quaternary Ammonium Salt and Tertiary Amine Bifunctionalized Polyacrylonitrile Fiber for Cooperatively Catalyzed Aza-Michael Addition

A series of novel polyacrylonitrile fiber catalysts modified with different ratio of quaternary ammonium salt (QA) to tertiary amine (TA) were screened for heterogeneously catalyzed aza-Michael addition in water. The best catalyst was found to be PANPQ-1F with a QA:TA ratio of 1:1, which can lead to high yield, excellent selectivity of solvent and great recyclability under optimized conditions. The special microenvironment of hydrophilic inner layer and hydrophobic surface layer of PANPQ-1F is conducive to the leaving of the product and the high conversion of the reaction. Based on the fact that appropriate microenvironment combined with the catalytic sites promoted the reaction, cooperative effect of QA and TA in the microenvironment of PANPQ-1F catalyst was proposed.

Lithium Chloride Catalyzed Aza-Michael Addition of Pyrazoles to α,β-Unsaturated Imides

A lithium chloride catalyzed aza-Michael reaction of pyrazoles to α,β-unsaturated imides has been developed. A range of aromatic and aliphatic α,β-unsaturated imides are found to be suitable for the established method, providing the corresponding aza-Michael adducts in up to 93% yields. The inexpensive catalyst, good substrate tolerance, and ease of scale-up make this procedure highly practical.

Graphene Oxide: A Metal‐Free Carbocatalyst for the Synthesis of Diverse Amides under Solvent‐Free Conditions

AbstractAn environmentally friendly, inexpensive, carbocatalyst, graphene oxide (GO) promoted efficient, metal‐free transamidation of various carboxamides with aliphatic, cyclic, and aromatic amines is demonstrated. The protocol is equally applicable to phthalimide, urea, and thioamide determining its adaptability. The oxygenated functionalities such as carbonyl (−C=O), epoxy (−O−), carboxyl (−COOH) and hydroxyl (−OH), present on graphene oxide surface impart acidic properties to the catalyst. The graphene oxide being heterogeneous in nature, work efficiently under solvent‐free reaction conditions providing desired products in good to excellent yields. The one‐pot synthesis of 2,3‐Dihydro‐5H‐benzo[b]‐1,4‐thiazepin‐4‐one moiety by GO catalyzed Aza Michael addition followed by intramolecular transamidation is also described. A plausible reaction mechanistic pathway involving H‐bonding is discussed. The graphene oxide can be recycled and reused up to five cycles without much loss in catalytic activity.magnified image

Scandium(III)-Catalyzed Aza-Michael Addition of in Situ Generated ortho-Quinone Methides with Amines: An Efficient Access to Betti Base Derivatives

Scandium(III)-Catalyzed Aza-Michael Addition of <i>in Situ</i> Generated <i>ortho</i>-Quinone Methides with Amines: An Efficient Access to Betti Base Derivatives

Gold-Catalyzed Synthesis of 2-Substituted Azepanes: Strategic Use of Soft Gold(I) and Hard Gold(III) Catalysts

Strategic use of both soft gold(I) and hard gold(III) catalysts provides azepanes from propargylic alcohols in one pot. Thus, propargylic alcohols in the presence of soft gold(I) catalyst (Ph3PAuNTf2) undergo a Meyer–Schuster rearrangement to give α,β-unsaturated ketones, which in turn undergo a gold(III) (AuBr3)-catalyzed aza-Michael addition to afford azepanes bearing a carbonyl group.

Cesium fluoride catalyzed Aza-Michael addition reaction in aqueous media

A green approach to the Aza-Michael addition reaction between an amine and α,β-unsaturated compounds has been achieved by conventional as well as non-conventional methods. The reaction is catalyzed by cesium fluoride (CsF) in aqueous media at ambient temperature to afford the product in excellent yield. Ultrasound irradiation has been used as a non-conventional energy source, which reduces the reaction time with improved product yield.

Silicon Tetrachloride Catalyzed Aza-Michael Addition of Amines to Conjugated Alkenes under Solvent-Free Conditions

The efficient and very simple conjugate addition of aromatic and aliphatic amines to α,β-unsaturated carbonyl compounds under solvent-free conditions in the presence of catalytic amount of silicon tetrachloride is reported. The reaction of aryl and alkyl amines with different Michael acceptors gave the corresponding Michael adducts with simple catalyst and good to excellent yields.

Copper(II)/Copper(I)-Catalyzed Aza-Michael Addition/Click Reaction of in Situ Generated α-Azidohydrazones: Synthesis of Novel Pyrazolone−Triazole Framework

A one-pot Cu(II)-catalyzed aza-Michael addition of trimethylsilyl azide to 1,2-diaza-1,3-dienes and Cu(I)-catalyzed 1,3-dipolar cycloaddition of in situ generated alpha-azidohydrazones with alkynes is reported. This process combining two consecutive steps with recycling of the catalyst (Cu(OAc)(2).H(2)O) represents a useful protocol for the smooth synthesis of novel pyrazolone-triazole derivatives.

Broad Scope Organocatalytic Aza-Michael Addition

A procedure for asymmetric cinchona alkaloid (1, 2) catalyzed aza-Michael addition of enones 3 and alkoxyamines 4 is reported. The scope of the reaction was demonstrated in several examples with different substituted substrates, affording products in moderate to good yields and good to excellent enantioselectivities. Moreover, the authors provide two possible activation modes. Both involve hydrogen-bonding interactions of the tertiary amine with alkoxyamines 4 and iminium-ion formation between the primary amine and the enones 3.

Y(NO3)3· 6H2O catalyzed aza-Michael addition of aromatic/hetero-aromatic amines under solvent-free conditions

The aza-Michael addition of weakly nucleophilic amines with α, β-unsaturated compounds like esters, nitriles and amides has been carried out efficiently using Y(NO3)3 · 6H2O as a novel catalyst under solvent-free conditions. The catalyst exhibited remarkable activity and the methodology was applicable to a wide variety of aryl/hetero-aryl amines having different steric and electronic properties giving high yields of desired adducts at ambient conditions.

Ceric Ammonium Nitrate Catalyzed aza-Michael Addition of Aliphatic Amines to α,β-Unsaturated Carbonyl Compounds and Nitriles in Water

Ceric ammonium nitrate (3 mol%) efficiently catalyzes the aza-Michael reaction of amines with α,β-unsaturated carbonyl compounds in water to produce the corresponding β-amino carbonyl compounds in good to excellent yields (55-99%) for most of the compounds under mild conditions. The reaction is procedurally simple and displays limited chemoselectivity, as aromatic amines were found to be unreactive.