Interlocked Molecules Using Olefin Metathesis

Citation

Guidry, Erin Nicole (2008) Interlocked Molecules Using Olefin Metathesis. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/XBXB-6931. https://resolver.caltech.edu/CaltechETD:etd-06252007-174232

Abstract

Olefin metathesis has been employed in the efficient syntheses of a [2]catenane with the templation being provided by the recognition between a secondary ammonium ion and a crown ether. In one approach, a crown ether precursor has been clipped around an NH2+ center situated in a macrocyclic ring, yielding the mechanically interlocked compound. In the other approach, the reversible nature of olefin metathesis allows for a magic ring synthesis to occur wherein two free macrocycles can be employed as the stationary materials, leading to the formation of the same [2]catenane.

A strategy for the formation of mechanically interlocked polymers is presented. Ring-closing olefin metathesis has been shown to provide a very high yielding route to [c2]daisy-chains suitably functionalized to allow their one-step conversion to bis-olefins which can be used as monomers in ADMET polymerizations to afford mechanically interlocked polymers. Metathesis, in two different guises is making a hitherto unreachable goal in synthesis a reality.

A method for the production of cyclic polyammonium ions is presented which utilizes a polymer cyclization of azide terminated linear polymer based on the “click” reaction. An azide terminated polymer was prepared using ROMP in the presence of chain transfer agents (CTA). Formation of cyclic polycateanes was explored utilizing the mutual recognition between secondary ammonium ions and crown ether macrocyles. The product of the RCM of linear crown ether dienes around cyclic polyammonium ions was investigated using 2D-DOSY.

The ring-opening metathesis polymerization of a [2]catenane was investigated, using both a cyclic metathesis catalyst and bulky metathesis catalysts for the formation of cyclic polycatenanes and polyrotaxanes respectively. While it was found that the [2]catenane monomer could function as a ROMP monomer, no interlocked polymers were observed as products from the polymerization. Linear impurities present in either or both the [2]catenane monomer and the metathesis catalysts are believed to be responsible for the formation of the non-interlocked polyether and free macrocycle. These results highlight the critical role of purity to the successful formation of cyclic or linear interlocked polymer using a ROMP process.

Thesis Files