Asymmetric Radical Cyclopolymerization of N-Allyl-N-phenylmethacrylamide in the Presence of SnCl₄ and l-Menthol

Abstract

Asymmetric induction was examined in the cyclopolymerization and cyclocopolymerization of N-allyl-N-phenylmethacrylamide (PAMA) with dimethyl 2,2′-azobis(isobutyrate) in benzene in the presence of L-menthol and SnCl4. Optical activity ([R]D ) -0.3 to -5.6) was observed for poly(PAMA)s formed in the radical polymerization of the PAMA/SnCl4/L-menthol system. The PAMA monomer unit was incorporated exclusively as a five-membered ring into the highly cyclized poly(PAMA)s (degree of cyclization (DC) ) 95-98%) obtained. The radical copolymerization of PAMA with methyl methacrylate in the presence of L-menthol and SnCl4 also gave optically active copolymers, the PAMA units of which were similarly highly cyclized (DC ) 90-94%) as a five-membered ring. The [R]D value of the copolymer increased up to [R]D ) -15.2 with increasing PAMA concentration in the feed. The much lower DC values (25-68%) of the PAMA monomer unit were observed for the copolymers formed in the copolymerization of the PAMA/styrene/L-menthol/SnCl4 system. However, the copolymers showed a considerable optical activity ([R]D ) -9.1 to -11.8).

Asymmetric cyclopolymerization ofN-tert-butyl-N-allylacrylamide in the presence of ?-cyclodextrin

“…Recently, ring construction in vinyl polymers has been proven to be particularly useful for stereochemical control in free‐radical polymerization 1–4. In an earlier article,5 we found that asymmetric induction is caused in the polymer main chain by radical cyclopolymerization of N ‐allyl‐ N ‐phenylmethacrylamide (APMA) in the presence of SnCl 4 and L ‐menthol as the chiral compound.…”

Asymmetric Radical Polymerization of Maleimides Using a Chiral Cobalt(II) Complex

“…A catalytic amount of chiral cobalt complex was shown to induce configurational chirality in a radical polymerization for the first time. The induction of configurational chirality to the polymer chain by radical polymerization using a chiral radical species is unprecedented though there are examples based on chiral monomer structure, chiral additives that presumably work as Lewis acids, , and a chiral inclusion complex . Further work is in progress in order to clarify the mechanism, to enhance the induction efficiency, and to find a way to control tacticity in the polymerization of more versatile monomers using a radical species.…”

Asymmetric Polymerization

“…The optical activity and the content of trans -structure in the main chain of the polymers were comparable to those of the polymers synthesized by using 1 . N -Phenyl -N -allylmethacrylamide ( 22 ) was shown to be a remarkable diene monomer for radical cyclopolymerization to give a polymer having fi ve -membered ring structures in the main chain with high cyclization selectivity of 95 -98% [66] . The enantioselective polymerization in the presence of SnCl 4 /( − ) -menthol gave optically active polymers with an optical rotation of [ α ] D − 5.6 ° .…”