142
H. Gröger
increasing tendency to use enantiomerically pure molecules rather than
racemates as chiral drugs, there is an increasing interest in developing
efficient synthetic technologies. Among conceivable approaches such as
multi-step syntheses starting from chiral pool molecules, resolution processes, and asymmetric catalytic technologies, the latter represents the
most attractive access for most cases. During recent decades an increasing tendency in industry was observed to apply asymmetric catalytic
processes (review: Blaser and Schmidt 2004). Supplementing the established catalytic technologies ‘Metal Catalysis’ (reviews: Katsuki 1999;
Jacobsen and Wu 1999) and ‘Biocatalysis’ (review: Drauz and Waldmann 2002), recently a third technology type emerged with ‘Organocatalysis’ (review: Berkessel and Gröger 2005). Seeking for new and
innovative technology platforms, the chemical industry shows an increasing interest in organocatalytic reactions as a potential solution for
large-scale applications.
2
Industrially Relevant Advantages of Organocatalysis
Organocatalysis offers several advantages not only with respect to its
synthetic range. Among “typical” advantages of organocatalysis, in particular with respect to large-scale applications, are favorable economic
data of many organocatalysts, the stability of organocatalysts as well as
the potential for an efficient recovery (Berkessel and Gröger 2005).
Many organocatalysts are easily available from cheap raw materials from the ‘chiral pool’ or simple derivatives thereof (e.g., alkaloids
and l-proline). In addition, for the majority of organocatalysts there are
no concerns regarding moisture sensitivity (which can represent a serious issue in the case of chiral metal complexes used as Lewis acid catalysts). Thus, special equipment for handling organocatalysts is often
not required. Recovery of organocatalysts after downstream processing
for re-use has also already been reported for organocatalysts in several
cases. Furthermore, immobilization represents a popular approach to
simplify separation of the catalyst from the reaction mixture. In contrast
to immobilized metal complexes (via a solid support-bound ligand),
leaching problems are not a critical issue when using organocatalysts
H. Gröger
increasing tendency to use enantiomerically pure molecules rather than
racemates as chiral drugs, there is an increasing interest in developing
efficient synthetic technologies. Among conceivable approaches such as
multi-step syntheses starting from chiral pool molecules, resolution processes, and asymmetric catalytic technologies, the latter represents the
most attractive access for most cases. During recent decades an increasing tendency in industry was observed to apply asymmetric catalytic
processes (review: Blaser and Schmidt 2004). Supplementing the established catalytic technologies ‘Metal Catalysis’ (reviews: Katsuki 1999;
Jacobsen and Wu 1999) and ‘Biocatalysis’ (review: Drauz and Waldmann 2002), recently a third technology type emerged with ‘Organocatalysis’ (review: Berkessel and Gröger 2005). Seeking for new and
innovative technology platforms, the chemical industry shows an increasing interest in organocatalytic reactions as a potential solution for
large-scale applications.
2
Industrially Relevant Advantages of Organocatalysis
Organocatalysis offers several advantages not only with respect to its
synthetic range. Among “typical” advantages of organocatalysis, in particular with respect to large-scale applications, are favorable economic
data of many organocatalysts, the stability of organocatalysts as well as
the potential for an efficient recovery (Berkessel and Gröger 2005).
Many organocatalysts are easily available from cheap raw materials from the ‘chiral pool’ or simple derivatives thereof (e.g., alkaloids
and l-proline). In addition, for the majority of organocatalysts there are
no concerns regarding moisture sensitivity (which can represent a serious issue in the case of chiral metal complexes used as Lewis acid catalysts). Thus, special equipment for handling organocatalysts is often
not required. Recovery of organocatalysts after downstream processing
for re-use has also already been reported for organocatalysts in several
cases. Furthermore, immobilization represents a popular approach to
simplify separation of the catalyst from the reaction mixture. In contrast
to immobilized metal complexes (via a solid support-bound ligand),
leaching problems are not a critical issue when using organocatalysts