The Application of a Recyclable Organocatalytic System to the Asymmetric Domino Michael/Henry Reaction in Aqueous Media

Mononitration of a Calix[4]arene Methylene Bridge: Synthesis and Preliminary Catalysis Performances of Bridging Chiral p-tert-Butylcalix[4]arenes with a Monoamino Bridge Substituent in a 1,3-Alternate Conformation

In order to prepare bridging chiral p-tert-butylcalix[4]crown-5 with a mononitro bridge substituent in a 1,3-alternate conformation, a mononitration method of calix[4]arene bridging methylene has been first developed with tert-butyl nitrite as a nitration reagent. The effects of solvent, reaction temperature, reaction time, and nitration reagent dosage on bridge mononitration have been deeply explored to obtain an optimal nitration condition. The facile nitration presents a new key for calix[4]arene bridge derivatization. After further modification and diastereoisomeric resolution, a pair of bridging chiral p-tert-butylcalix[4]arenes with a monoamino bridge substituent were produced from the bridge-mono-nitrated calix[4]arene. Their preliminary catalysis results in the Henry reaction show good catalytic activities (up to 95% yield) and still low but obviously enhanced enantioselectivities (up to 22.3% ee from 7a, 6% ee from 1), which confirms that the structural transformation indeed improves asymmetric catalysis performances of bridging chiral calix[4]crown-5 amines in a 1,3-alternate conformation.

Waste-to-useful: a biowaste-derived heterogeneous catalyst for a green and sustainable Henry reaction

Owing to the depletion of resources coupled with increasing waste generation, the conversion of waste biomass to value-added materials has gained interest.

Polymer supported DMAP: an easily recyclable organocatalyst for highly atom-economical Henry reaction under solvent-free conditions

Polymer supported catalysts are regarded as a borderline class of catalysts, which retains the advantages of homogeneous catalysts while securing the ease of recovery by simple filtration and workup of heterogeneous systems.

Amide functionalized metal–organic frameworks for diastereoselective nitroaldol (Henry) reaction in aqueous medium

The metal–organic frameworks [Zn₂(L)₂(1,4-BDC)]_n·2n(DMF) (L = 4-(pyridin-4-ylcarbamoyl)benzoate; BDC = benzenedicarboxylate) and [Cu(L)₂]_n·4n(DMF)·n(H₂O) work as catalysts for the diastereoselective nitroaldol reaction in aqueous medium.

Linear dialdehydes as promising substrates for aminocatalyzed transformations

Linear dialdehydes: This article summarizes the recent utilization of linear dialdehydes as appropriate substrates for amine catalyzed cascade/domino transformations.

Sulfonated Schiff base dinuclear and polymeric copper(ii) complexes: crystal structures, magnetic properties and catalytic application in Henry reaction

Aqueous medium syntheses and nitroaldol catalytic studies of three pseudohalide bridged copper(ii) complexes characterized by single crystal X-ray structure analysis and variable temperature magnetic studies are reported.

Catalytic MBH reaction of β-substituted nitroalkenes with azodicarboxylates

An unprecedented N-heterocyclic carbene (NHC) catalyzed Morita-Baylis-Hillman (MBH) reaction of β-substituted nitroalkenes and azodicarboxylates has been developed. Both β-aryl and β-alkyl nitroalkenes worked well for the reaction using 5 mol% of NHC catalyst, giving the desired α-hydrazino-α,β-unsaturated nitroalkenes in good to excellent yields.

Asymmetric Synthesis of Substituted Thiolanes through Domino Thia-Michael-Henry Dynamic Covalent Systemic Resolution using Lipase Catalysis

Dynamic systems based on consecutive thia-Michael and Henry reactions were generated and transformed using lipase-catalyzed asymmetric transformation. Substituted thiolane structures with three contiguous stereocenters were resolved in the process in high yields and high enantiomeric excesses.

Enantioselective Synthesis of Spiro[cyclohexane-1,3'-indolin]-2'-ones Containing Multiple Stereocenters via Organocatalytic Michael/Aldol Cascade Reactions

Organocatalytic reactions of 3-olefinic oxindoles and pentane-1,5-dial were investigated to provide access to substituted spirocyclohexane oxindoles via Michael/Aldol cascade reactions. Of particular interest, we have examined the stereochemical outcome of electron withdrawing and electron-donating groups on the oxindole ring nitrogen. Interestingly, we have observed that the N-protecting group on the oxindole has critical effect on aldol ring closure leading to ultimate stereochemical outcome of the hydroxyl center. The overall process is quite efficient and afforded products with multiple stereocenters in high yields and excellent enantioselectivities (>99% ee).

One-pot sequential organocatalysis: highly stereoselective synthesis of trisubstituted cyclohexanols

A highly diastereoselective (d.r. >99:1) and enantioselective (ee value up to 96%) synthesis of trisubstituted cyclohexanols was achieved by using a one-pot sequential organocatalysis that involved a quinidine thiourea-catalyzed tandem Henry-Michael reaction between nitromethane and 7-oxo-hept-5-en-1-als followed by a tetramethyl guanidine (TMG)-catalyzed tandem retro-Henry-Henry reaction on the reaction products of the tandem Henry-Michael reaction. Through a mechanistic study, it has also been demonstrated that similar results may also be achieved with this one-pot sequential organocatalysis by using the racemic Henry product as the substrate.