DOI: 10.1002/chem.200801495
Rational Design of Sugar-Based-Surfactant Combined Catalysts for
Promoting Glycerol as a Solvent
Ayman Karam,[a] Nicolas Villandier,[a] Mathieu Delample,[a, c] Carmen Klein Koerkamp,[b]
Jean-Paul Douliez,[c] Robert Granet,[b] Pierre Krausz,[b] Joꢀl Barrault,[a] and
FranÅois Jꢁrꢂme*[a]
Since the last decade, catalysis in water has attracted a lot
of attention.[1] Indeed, it has been well established that the
design of catalytic processes in water offers indisputably en-
vironmentally friendlier pathways. However, to get over the
reactivity of water and the low solubility of most of organic
substrates in water, researchers, especially Kobayashiꢀs
group, have developed a new concept based on the use of
surfactant combined catalysts (SCCs).[2] These SCCs are
able to form stable emulsions in water, which results in a
considerable increase in both the reaction selectivity and the
reaction rate. However, even if spectacular results were re-
ported under micellar catalysis, emulsification of the reac-
tion mixture unfortunately makes extraction of the reaction
products highly difficult. Indeed, in most cases assistance of
an organic solvent is required, which considerably decreases
the environmental benefit of using water as solvent.[2,3] It
has to be noted that cyclodextrins appear to be a good alter-
native to overcome this issue because these carbohydrates
avoid emulsification of the reaction media while maintaining
a good diffusion of the organic reactants in the aqueous
phase.[4] However, even if extraction of the reaction prod-
ucts was considerably facilitated, the use of highly hydro-
phobic substrates is still subject to strict limitations.
Seeking new improvements for catalysis in water, we
found that using glycerol as a solvent offers as many advan-
tages as water, and our aim herein is to convince the reader
that glycerol could be familiarly considered as “organic
water”. Indeed, like water, glycerol is natural, highly hydro-
philic, nontoxic (LD50 (oral rat)=12600 mgKgÀ1), abun-
dant (1.5MtyearÀ1 in 2008), biodegradable and very cheap
(ꢀ1E/kg).[5] Moreover, compared with water, glycerol has a
higher boiling point (2908C) and a lower vapour pressure
(<1 mmHg at 508C), which makes the development of cata-
lytic processes at temperatures around 1008C technically
easier. Surprisingly, despite having very similar solvent prop-
erties to those of water, only pioneer catalytic studies have
been investigated in glycerol.[6] This tendency might arise
from 1) the very low solubility of organic substrates in glyc-
erol and 2) the intrinsic reactivity of this natural polyol,
which leads to the formation of side products.
Herein, we wish to show that the use of SCCs allow all
drawbacks to the use of glycerol as a solvent to be overcome
by favouring a better diffusion of organic substrates in the
glycerol phase and creating some hydrophobic environments
inside which it is possible to inhibit the reactivity of glycerol.
Moreover, we found that micellar catalysis in glycerol offers
a remarkable advantage compared with water because the
emulsions formed in glycerol were found to be unstable.
Consequently, two phases rapidly formed at the end of the
reaction, which allowed an easy extraction of the reaction
products without the assistance of any organic solvents, as is
generally the case in water.
[a] A. Karam, Dr. N. Villandier, M. Delample, Dr. J. Barrault,
Dr. F. Jꢁrꢂme
Laboratoire de Catalyse en Chimie Organique
Universitꢁ de Poitiers/CNRS
40 avenue du recteur Pineau, 86022 Poitiers (France)
Fax : (+33)549-453-349
In the first set of experiments, we investigated the base-
catalyzed ring opening of 1,2-epoxydodecane with dodeca-
noic acid as a model reaction. For the reasons mentioned
above, when this reaction was performed at 1108C in glycer-
ol by using conventional basic catalysts, such as chitosan,
silica-supported methylamine, ZnO or K2CO3, the reaction
rate was low and total conversion only occurred after 18 h
(Table 1, entries 2–5). Similarly, the selectivity of the reac-
tion was poor because glycerol ethers that resulted from the
[b] C. K. Koerkamp, Dr. R. Granet, Prof. P. Krausz
Laboratoire de Chimie des Substances Naturelles
Facultꢁ des Sciences et Techniques
La Borie, 123 avenue Albert Thomas 87060 Limoges (France)
[c] M. Delample, Dr. J.-P. Douliez
INRA Nantes, BIA ꢁquipe Interfaces et Systꢃmes Dispersꢁs
Rue de la Gꢁraudiꢃre, 44316 Nantes (France)
Supporting information for this article is available on the WWW
10196
ꢄ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 10196 – 10200