Microwave-Assisted and Efficient Solvent-free Knoevenagel Condensation. A Sustainable Protocol Using Porous Calcium Hydroxyapatite as Catalyst

Abstract

A sustainable Knoevenagel condensation of a series of aldehydes with malononitrile and ethyl cyanoacetate is described. The process is based on the combination of microwave activation and hydroxyapatite catalysis under solvent-free conditions. Products are obtained in and high yields after short reaction times. The effects of the specific surface of porous calcium hydroxyapatite and microwave activation are discussed.

Metal Phosphate-Supported Pt Catalysts for CO Oxidation

“…In the literature, some metal carbonates, phosphates, and sulfates have been used as supports to load metals [2]. From the examples on the catalytic applications of metal phosphate-based catalysts cited in the Introduction section [4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,…”

Potassium Fluoride/ K10-montmorillonite Nanostructure as a Green and Reusable Catalyst Under mild Reaction Conditions for the Knovenagel Condensation

“…This reaction is a practical method to achieve fine chemical intermediates and therapeutic and pharmacological products [1][2][3] . Owing to their impor tance from an industrial, pharmacological and synthetic point of view a great number of methods for the Knoevenagel condensation have been developed using various Lewis acids/bases under ultrasound and microwave irridiation, using green solvent like water or ionic liquid, and grindstone method under solvent-free condition [4][5][6][7][8][9][10][11][12] . However, most of the reported reagents suffer from disadvantages such as high cost reagent, tedious work-up, environmental limitations, disposal problems and so on.…”

2.14 Other Condensation Reactions (Knoevenagel, Perkin, Darzens)

“…43 solvent-less conditions. 44 Hydroxyapatite showed high thermal stability and can be recovered by simple filtration and reused for at least ten times without the loss of activity.…”