Self-Assembly in Organic Synthesis

A logical approach to the establishment of the concept of self-assembly processes, which mimic those found in nature, is proposed for the synthesis of ordered molecular and polymolecular arrays from readily available starting materials. The order, which characterises the unnatural products that result, could lead to the development of new materials with functions, as well as forms. The synthetic strategy we have adopted relies upon the use of mechanically interlocked molecular components, in the shape of catenanes and rotaxanes, to provide the means for transposing, in a reasoned way, the knowledge and experience gained from the study of relatively small supramolecular host-guest systems to much larger polymolecular arrays, ordered and stabilised by the mechanical interwining and threading of molecules. In pursuit of these long term objectives, a number of highly efficient template-directed syntheses of catenanes and rotaxanes have been executed. They illustrate the growing potential of molecular self-assembly processes in the realm of organic synthesis. In essence, we argue that there are inherently simple ways of making apparently complex unnatural products from appropriate substrates without the need for reagent control or catalysis. 1. Introduction 1.1. Preamble 1.2. Self-Assembly Processes in Nature 1.3. Evolving a Synthetic Strategy 1.4. Template-Directed Syntheses in Concept 1.5. Self-Assembling Unnatural Products 2. Rotaxanes and Pseudorotaxanes Made to Order 2.1. [2]Rotaxanes 2.2. Template-Directed Syntheses in Action 2.3. Self-Assembling Pseudorotaxanes 2.4. The Molecular Shuttle 2.5. Self-Assembling More Pseudorotaxanes 3. More Catenanes Made to Order 3.1. From Benzo to Naphtho Rings 3.2. Expanding the Charged Ring 3.3. Expanding the Neutral Ring 4. Self-Assembly - What are the Limits? 5. Reflections