ROMP of Norbornene Monomers Carrying Nonprotected Amino Groups with Ruthenium Catalyst

Abstract

Amino acid-derived novel norbornene monomers (1a-2b) having nonprotected amino groups, together with tert-butoxycarbonyl (Boc) protected ones (1a-Boc-2b-Boc) were synthesized and polymerized by ring-opening metathesis polymerization using the Grubbs second generation ruthenium catalyst. The l-alanine-derived endo,endo-monomer 1a with amino groups gave no polymer, while the exo,exo-isomer 1b gave a polymer by raising the catalyst concentration. N-Methyl-l-alanine-derived 2a and 2b carrying secondary amino groups gave polymers in yields higher than 1a and 1b. On the other hand, Boc-protected 1a-Boc-2b-Boc gave the polymers in almost quantitative yields irrespective of the stereo structure (endo, exo) as well as the absence and presence of methyl group at the nitrogen atom. 1H−1H COSY NMR spectroscopic analysis and molecular mechanics calculation indicated that the polymers were syndiotactic.