DBU: a highly efficient catalyst for one-pot synthesis of substituted 3,4-dihydropyrano[3,2-c]chromenes, dihydropyrano[4,3-b]pyranes, 2-amino-4H-benzo[h]chromenes and 2-amino-4H benzo[g]chromenes in aqueous medium

A series of easily prepared Lewis basic ionic liquids were developed for cyclic carbonate synthesis from epoxide and carbon dioxide at low pressure without utilization of any organic solvents or additives. Notably, quantitative yields together with excellent selectivity were attained when 1,8-diazabicyclo[5.4.0]undec-7-enium chloride ([HDBU]Cl) was used as a catalyst. Furthermore, the catalyst could be recycled over five times without appreciable loss of catalytic activity. The effects of the catalyst structure and various reaction parameters on the catalytic performance were investigated in detail. This protocol was found to be applicable to a variety of epoxides producing the corresponding cyclic carbonates in high yields and selectivity. Therefore, this solvent-free process thus represents an environmentally friendly example for the catalytic conversion of carbon dioxide into value-added chemicals by employing Lewis basic ionic liquids as catalyst. A possible catalytic cycle for the hydrogen bond-assisted ring-opening of epoxide and activation of carbon dioxide induced by the nucleophilic tertiary nitrogen of the ionic liquid was also proposed.

Lewis Basic Ionic Liquids-Catalyzed Conversion of Carbon Dioxide to Cyclic Carbonates

Highly efficient conversion of carbon dioxide catalyzed by polyethylene glycol-functionalized basic ionic liquids

Ionic Liquids: Applications and Perspectives

Data published in the last 10 years on the use of the aza-Michael reaction in organic synthesis are described systematically. The attention is focused on environmentally friendly processes following green chemistry principles and on methods for the synthesis of compounds that are difficult to access by other routes.

https://iopscience.iop.org/article/10.1070/RC2011v080n03ABEH004162/pdf

Aza-Michael reaction: achievements and prospects

Aza-Michael addition of aliphatic or aromatic amines to α,β-unsaturated compounds catalyzed by a DBU-derived ionic liquid under solvent-free conditions

An efficient, clean and facile protocol for the Knoevenagel condensation of aromatic aldehydes with active methylene compounds catalysed by task specific ionic liquid 1,8-diazabicyclo[5.4.0]-undec-...

Green and efficient Knoevenagel condensation catalysed by a DBU based ionic liquid in water

The DBU (1,8-Diazabicyclo[5.4.0]undec-7-ene) derived task-specific ionic liquids [DBU][Lac] (1,8-diazabicyclo[5.4.0]-undec-7-en-8-ium lactate), [DBU][Ac] (1,8-diazabicyclo[5.4.0]-undec7-en-8-ium acetate) and [DBU][Tfa] (1,8-diazabicyclo[5.4.0]-undec-7-en-8-ium trifluoroacetate) were synthesized. Among the three novel ionic liquids, [DBU][Lac] was found to have the highest catalytic activity for aza-Michael addition of aromatic amines to α,β-unsaturated ketones. The protocol can give good to excellent products yields and has advantages such as readily work-up and good reusability, which makes this method quite attractive.

Green and efficient aza-Michael additions of aromatic amines to α,β-unsaturated ketones catalyzed by DBU based task-specific ionic liquids without solvent

The invention relates to a green efficient method for condensing aromatic aldehydes and active methylene compounds. The method comprises: taking ionic liquid as a catalyst; subjecting aromatic aldehydes and active methylene compounds to catalytic condensation reaction at room temperature under normal pressure; filtering the obtained product to obtain corresponding condensation product water serving as a reaction medium; stirring the obtained product at room temperature; and finishing reaction and then directly filtering the obtained product so as to obtain products. Filtrate containing aqueous phase of the ionic liquid can be repeatedly used ten times as a catalytic reaction system, and reaction yield does not drop. The method has the advantages of simple operation, high yield, good use repeatability of the catalytic reaction system, mild reaction conditions and good prospects for industrialization.

Novel method for condensing aromatic aldehydes and active methylene compounds through catalysis of functional ionic liquid

The invention relates to a method for generating beta-aminoketone, ester, nitrile and amide derivatives by performing aza-Michael addition on amine substances and electron-deficient alkenes through an efficient environment-friendly catalyst under solvent-free mild (room temperature) reaction conditions. The method comprises the steps of taking ionic liquid as the catalyst, subjecting amine substances and electron-deficient alkenes to aza-Michael addition at room temperature under normal pressure and obtaining corresponding beta-aminoketone, ester, nitrile and amide derivatives. The ionic liquid is repeatedly used five times, and reaction yield does not obviously drop. The method has the advantages of simple operation, high yield, good using repeatability of the catalytic reaction system, mild reaction conditions and good prospects for industrialization.

Wei-Dong Ye

Papers

Aza-Michael addition of aliphatic or aromatic amines to α,β-unsaturated compounds catalyzed by a DBU-derived ionic liquid under solvent-free conditions

Green and efficient Knoevenagel condensation catalysed by a DBU based ionic liquid in water

Green and efficient aza-Michael additions of aromatic amines to α,β-unsaturated ketones catalyzed by DBU based task-specific ionic liquids without solvent

Novel method for condensing aromatic aldehydes and active methylene compounds through catalysis of functional ionic liquid

Novel method for preparing beta-aminoketone, ester, nitrile and amide derivatives through catalysis of functional ionic liquid