Cyclopolymerization - XXVI. Repeating unit structure of cyclopolymers derived from N-substituted-N-allyl-2-(methoxycarbonyl)allylamines and mechanismof intramolecular cyclization

NMR studies on completely cyclized polymers derived from N-substiluted-N-al lyl-2- (methoxycarbonyl)allylamines (1) were undertaken to determine the re peat cyclic unit. NMR techniques employed are two-dimensional INADEQUATE (I ncredible Natural Abundance DoublE QUAntum Transfer Experiment), DEFT (Dist ortion Enhancement by Polarization Transfer) measurements, and those under suppressed nuclear Overhauser effect. These studies along with the comparis on of the spectra of poly(1) with those of related compounds revealed that the poly(1) consists of two sets of five-membered rings. The main chain met hylene carbons attached to the ring has a trans configuration for one of th em and a cis arrangement for the other. The former was found to be a main c omponent. The value 4.5 kJ/mol as the difference of the activation energy f or the formation of the respective configuration, E-cis - E-trans, was obta ined by the investigation of temperature effect. Comparison of these result s with those reported so far for polymers with similar structures led to th e conclusion that five-membered ring formation could be interpreted by a ki netic mechanism as in the radical cyclization reactions in low molecular we ight compounds. (C) 1999 Elsevier Science Ltd. All rights reserved.