300
M. Benaglia
1
Introduction
Catalysts are used in the production of a large variety of chemicals and
fuels, as demonstrated by the fact that catalyst-based manufacturing
accounts for about 60% of chemical products and 90% of processes
(Senkan 2001). These numbers will likely increase in the future, considering all the advantages of a catalytic process: it requires only small
amount of a ‘smart’ molecule to produce a large quantity of the desired
compound; the catalyst usually allows operation under mild reaction
conditions; also the economic benefits of an efficient catalytic process
are enormous since it is less capital-intensive, has lower operating costs,
produces products of higher purity and fewer by-products. In addition,
catalysts provide important environmental benefits.
These undoubted positive features are very attractive also for the
preparation of chiral compounds. Demand for enantiomerically pure
compounds is continuously increasing, not only for use in pharnaceuticals but also in other fields such as agrochemicals, flavour and aroma
chemicals, and speciality materials. Recent, strict government regulations that require the individual evaluation of all the possible stereoisomers of a compound and the commercialization of a chiral product only
as single enantiomer have called for further improvements in the stereoselective synthesis of chiral compounds. In this context it is surprising
how relatively few enantioselective catalytic reactions are used on an industrial scale today (Blaser 2003). This is even more difficult to understand if one thinks about the impressive progress made over the last few
years in the field of enantioselective catalysts, where hundreds of catalytic transformations of great chemical and stereochemical efficiency
have been developed.
So the obvious question is this: Why has the application of enantioselective catalysis to the fine chemicals industry, of potentially great
economic and environmental interest, not been widely pursued on large
scale? It is true that different issues must be addressed: firstly there is
the cost of the chiral catalyst, but other problems must also be considered, such as general applicability; many of the very selective catalysts have been developed for reactions with selected model substrates
but not tested on differently functionalized molecules. In addition, for
many catalysts little information is available on catalyst selectivity, ac-
M. Benaglia
1
Introduction
Catalysts are used in the production of a large variety of chemicals and
fuels, as demonstrated by the fact that catalyst-based manufacturing
accounts for about 60% of chemical products and 90% of processes
(Senkan 2001). These numbers will likely increase in the future, considering all the advantages of a catalytic process: it requires only small
amount of a ‘smart’ molecule to produce a large quantity of the desired
compound; the catalyst usually allows operation under mild reaction
conditions; also the economic benefits of an efficient catalytic process
are enormous since it is less capital-intensive, has lower operating costs,
produces products of higher purity and fewer by-products. In addition,
catalysts provide important environmental benefits.
These undoubted positive features are very attractive also for the
preparation of chiral compounds. Demand for enantiomerically pure
compounds is continuously increasing, not only for use in pharnaceuticals but also in other fields such as agrochemicals, flavour and aroma
chemicals, and speciality materials. Recent, strict government regulations that require the individual evaluation of all the possible stereoisomers of a compound and the commercialization of a chiral product only
as single enantiomer have called for further improvements in the stereoselective synthesis of chiral compounds. In this context it is surprising
how relatively few enantioselective catalytic reactions are used on an industrial scale today (Blaser 2003). This is even more difficult to understand if one thinks about the impressive progress made over the last few
years in the field of enantioselective catalysts, where hundreds of catalytic transformations of great chemical and stereochemical efficiency
have been developed.
So the obvious question is this: Why has the application of enantioselective catalysis to the fine chemicals industry, of potentially great
economic and environmental interest, not been widely pursued on large
scale? It is true that different issues must be addressed: firstly there is
the cost of the chiral catalyst, but other problems must also be considered, such as general applicability; many of the very selective catalysts have been developed for reactions with selected model substrates
but not tested on differently functionalized molecules. In addition, for
many catalysts little information is available on catalyst selectivity, ac-