Dicalcium phosphate dehydrate DCPD as a highly efficient and reusable catalyst for Knoevenagel condensation

Article abstract of DOI:10.1080/00397911.2016.1142565

We have described the catalytic activities of dicalcium phosphate dihydrate (DCPD) in the condensation reaction of various substituted benzaldehydes with active methylene compound malononitrile. The influences of reaction conditions on the corresponding c

Full text of DOI:10.1080/00397911.2016.1142565

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Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: http://www.tandfonline.com/loi/lsyc20
Dicalcium Phosphate Dehydrate DCPD as a Highly
Efficient and Reusable Catalyst for Knoevenagel
Condensation
Zakaria Benzekri, Kamal El Mejdoub, Said Boukhris, Brahim Sallek, Brahim
Lakhrissi & Abdelaziz Souizi
To cite this article: Zakaria Benzekri, Kamal El Mejdoub, Said Boukhris, Brahim Sallek, Brahim
Lakhrissi & Abdelaziz Souizi (2016): Dicalcium Phosphate Dehydrate DCPD as a Highly Efficient
and Reusable Catalyst for Knoevenagel Condensation, Synthetic Communications, DOI:
10.1080/00397911.2016.1142565
To link to this article: http://dx.doi.org/10.1080/00397911.2016.1142565
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Date: 11 February 2016, At: 08:33

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Dicalcium phosphate dehydrate DCPD as a highly efficient and reusable catalyst for
Knoevenagel condensation
Zakaria Benzekri1, Kamal El Mejdoub2, Said Boukhris1, Brahim Sallek2, Brahim
Lakhrissi2, Abdelaziz Souizi1
1Laboratoire de Chimie Organique, Organométallique et Théorique. Faculté des Sciences,
Université Ibn Tofaïl, Kenitra, Morocco 2Laboratoire d’Agroressources et Génie des
Procédés. Faculté des Sciences, Université Ibn Tofaïl, Kenitra, Morocco
Corresponding author Said Boukhris E-mail: nsboukhris@yahoo.com
Supplemental data for this article can be accessed on the publisher’s website.
Abstract
We have described the catalytic activities of dicalcium phosphate dihydrate (DCPD) in
the condensation reaction of various substituted benzaldehydes with active methylene
compound malononitrile. The influences of reaction conditions on the corresponding
catalytic behavior have been investigated. The results showed that the DCPD exhibited
high catalytic activity, versatility and it can be recycled without significant loss of its
activity for the condensation reactions, that which accounts for the material as a
promising new type of heterogeneous catalyst for the condensation reactions. Meanwhile,
the catalytic results of DCPD compared favorably with those of other materials for
Knoevenagel reactions reported previously.
KEYWORDS: Dicalcium phosphate dihydrate, Heterogeneous catalysis, Knoevenagel
reaction, Room temperature
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INTRODUCTION
The Knoevenagel condensation reaction is a useful transformation that has been widely
employed for carbon–carbon bond formation in organic synthesis.[1] In recent years, a
wide array of catalysts, including Lewis acids,[2] solid bases,[3] ionic liquids,[4]
organometallic catalysts,[5] Sevelamer[6] and solid supported catalysts[7,8] have been used
to catalyze the Knoevenagel condensation reaction. However, most of these methods
suffer from one disadvantage or another, such as using hazardous and carcinogenic
solvents, high catalyst loading or non-recoverable catalysts that sometimes contain toxic
metals. Therefore, there is a great need for new catalytic methods that do not have these
problems. Functional phosphates catalysts have recently attracted significant attention for
organic synthesis because of their ease of recovery, reuse, and simplified product
isolation and purification. Using phosphates catalysts is an efficient way to achieve
economically advantageous and environmentally friendly processes. . The Knoevenagel
condensation is a powerful method to construct a carbon–carbon bond and has been
widely used in the production of fine chemicals, such as cosmetics, drugs, and other
substances.[9-11] A wide range of catalysts have recently been used in the Knoevenagel
condensation.[12-28] but several disadvantages remain regarding to the use of these
catalysts, such as difficulties in catalyst recovery and reuse, longer reaction time, or harsh
reaction conditions.Therefore, the study of a catalyst for Knoevenagel condensation
based on a functional phosphate catalyst is challenging.
The phosphate compound is an environmentally friendly solid material with excellent
mechanical strength and stability. Several heterogeneous catalysts catalysts have been
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reported for the Knoevenagel condensation reaction, but few of them are based on
phosphate calcium catalyst. Herein, we would like to report our work on this dicalcium
phosphate dihydrate (DCPD) to catalyze the Knoevenagel condensation reaction with
high efficiency and excellent reusability. The catalyst can be easily recovered and still
retains catalytic activity. The optimal reaction conditions were obtained after screening
the catalyst loading, reaction time, solvent and temperature for the Knoeveangel
condensation reaction between benzaldehyde and malononitrile.
RESULTS AND DISCUSSION
General Information For The Catalyst
Dicalcium phosphate dihydrate CaHPO4, 2H2O (DCPD) can be obtained in aqueous
medium eitherby neutralization of phosphoric acid by calcium hydroxide,[29] or by double
decomposition of a calcium salt and a phosphate salt.[30] The crystal structure of this
compound has been described by Jones[31] through the X-ray diffraction and by Curry[32]
using the neutron diffraction. DCPD crystallizes in the monoclinic system (space group:
Ia); crystallographic parameters are: a = 5.812 Å, b = 15.180 Å, c = 6.239 Å and = 116
25.
A schematic representation of its structure is given in Figure 1. The structure of DCPD
consists of corrugated sheets consist of Ca-PO4-Ca-Ca-Ca-PO4 chains oriented parallel.
The crystals are in the form of platelets, and sometimes in the form of needles.[33]
3