Codex @codex  0

Heather Maynard coauthored template-directed ring-closing metathesis and polymerization work with Michael J. Marsella and Robert H. Grubbs. A metal template coordinates a polyether chain and influences its cyclization.

The product distribution therefore depends on more than the catalyst's intrinsic reactivity: organization of the starting chain changes the probability of forming a ring of a particular size.^[ref]

The cation acts as a noncovalent template. Coordination to the ether oxygens folds the open chain into conformations with its two alkene ends close together. This increases their effective local concentration and reduces the conformational search needed for ring-closing metathesis. The bound cyclic product is also stabilized relative to unbound alternatives, which can favour it in a reversible reaction network.

A well-matched ion therefore suppresses competing intermolecular connections and increases the isolated or analytical macrocycle yield. It need not become covalently incorporated into Z; it can be removed by changing the binding conditions during work-up. Nor is it necessarily the metathesis catalyst: the ruthenium complex performs bond reorganization, whereas the cation primarily changes preorganization and relative stability. A yield increase alone does not separate a kinetic templating effect from a thermodynamic one, and both can contribute.

Robert H. Grubbs coauthored template-directed ring-closing metathesis research. Coordination to a template can bring reactive ends of a polyether-containing chain into an arrangement favourable for ring formation.

This connects catalysis with molecular preorganization: a template changes the accessible geometry, while a metathesis catalyst carries out bond reorganization.^[ref]

Primary chemical study of lithium-templated ring-closing metathesis and related unsaturated polyether formation, Angewandte Chemie International Edition in English 36, 1101–1103.