Concepts of Nature in Organic Synthesis: Cascade Catalysis and Multistep Conversions in Concert

Abstract

The development of cascade conversions (i.e. combined (catalytic) reactions without intermediate recovery steps as taking place in living cells) is considered as one of the important future directions for carrying out sustainable organic syntheses with inherently safer designs. It will drastically reduce operating time and costs as well as consumption of auxiliary chemicals and use of energy. Production of waste for multistep syntheses might ultimately reach the level of well below 1 kg per kg of product. The concept of cascade conversions is demonstrated by a representative selection of illustrative, mostly catalytic, examples on laboratory as well as on pilot or industrial scale and discussed within the strategic context of new synthesis methodology as required by present developments in life sciences industries. Full exploitation of such multistep syntheses and catalysis will require the development of novel, mutually compatible, organic and biosynthetic methods and procedures. Eventually a full integration of organic synthesis and biosynthesis can be envisaged. Syntheses requiring a smaller range of reaction parameters and reagents but a more intricate array of efficient catalysts might be expected. Integration with in situ product separation techniques will become mandatory, preferably by continuous processing.