Supramolecular assistance to synthesis

Intermolecular interactions and metal coordination have in particular been used very effectively for the synthesis of novel organic and inorganic entities such as ro- 

Inorganic templating and self-assembly provide coordination compounds whose geometries make possible the synthesis of complex structures, namely of cyclic multiporphyrin arrays [9.13a, 9.179], of inorganic rotaxanes [9.97a, 9.180], of multi-catenates and catenands (see 181) [8.281, 8.282] and even of molecular knots (see 182) [8.282, 9.77, 9.181] (in 181 and 182 a) with, b) without Cu(l) template). 

One may expect that by taking advantage of suitably designed supramolecular features it will be possible to generate a variety of highly complex architectures that would not be accessible otherwise (or only with low efficiency). Such supramolecular assistance adds a new direction with powerful means to organic synthesis. 

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One may imagine extending this type of methodology to reactivity, catalysis and transport by generating suitable libraries for the discovery of novel synthetic reagents, reactions, catalysts [9.176c] and carriers as well as for the exploration of product preparation through supramolecular assistance to synthesis (see Section 9.6). 

During the past 20 years, mechanically interlocked molecules, known as catenanes and rotaxanes, many of them redox-active, have become readily accessible using template-directed protocols that rely upon the precepts of molecular recognition and self-assembly and the tenets of supramolecular assistance to covalent synthesis. By incorporating different recognition units with dissimilar redox properties into appropriate components, these compounds can often be induced to switch hysteretically between ground and metastable co-con-... 

Supramolecular assistance to covalent synthesis has become an important tool as an alternative synthetic route to prepare stereocontrolled compounds either in solution or in the solid state. Chemical synthesis performed in the solid state provides an interesting green alternative for the preparation of novel and traditional products. ... 

Another aspect of synthetic supramolecular chemistry is the supramolecular assistance to molecular synthesis, in which intermolecular non-covalent interactions are used to bring molecular components in appropriate position and orientation in the intermediate steps of the synthesis of a molecular compound [17]. In both these aspects the self-assembly is the main actor [32-34]. 

The contribution of supramolecular chemistry to chemical synthesis has two main aspects the production of the non-covalent supramolecular species themselves, that is directly expressed in self-assembly processes, and the use of supramolecular features to assist in the synthesis of covalent molecular structures. 

Templated synthesis is a timely research area where molecular and supramolecular sciences meet. Moreover, it represents an emerging interface between chemistry, biology, and materials sciences. This multi-author monograph includes authoritative contributions from ten leading research laboratories involved in the development of novel template-assisted organic synthesis at this interface. It demonstrates how non-covalent and covalent templates are successfully applied to control the rate and the regio- and stereoselectivity of molecular and supramolecular organic reactions. 

Rint P. Sijbesma (left) did his graduate research with professor Roeland Nolte at the University of Nijmegen the focus was on synthetic receptor molecules. From 1992 to 1993 he worked as a postdoctoral research assistant with professor Fred Wudl (University of California, Santa Barbara) on the synthesis of water-soluble C6o-derivatives. In 1993 he took his present position as assistant professor in the laboratories of professor E. W. Meijer, where he is working in the field of supramolecular polymer chemistry. 

The classical thermochemical approach has also already been applied to special template-assisted chemical reactions like the template-directed synthesis of oligonucleotides [260], for which a detailed system of kinetic elementary steps has been derived and solved. Other examples are the thermochemical model for the assessment of cooperativity in self-assembly processes proposed in Ref. [261, 262] and for the quantitative description of multicomponent self-assembly processes of polymetallic helicates [263, 264]. More thermochemical approaches applied within particular fields of supramolecular chemistry will be mentioned in the following. 

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