Asymmetric synthesis of optically active di‐isotactic polymers from cyclic monomers

Abstract

A new asymmetric synthesis of polymers is described; it was obtained from monomers which do not contain asymmetric carbon atoms.The polymerization, in the presence of asymmetric cationic catalysts, of an unsaturated cyclic compound, bensofuran, by opening of the double bond of the furan ring, led to polymers having high optical activity.The rotation dispersion curve, which shows a maximum a t 303 my ([MI = -800) is here shown. Each monomeric unit of these polymers contains two carbon atoms in the chain, which are asymmetric, even if considered in their immediate surrounding.Optically active polybenzofurans do not remarkably contain asymmetric end-groups deriving from the catalyst. The asymmetric synthesis may therefore be related to the orienting effect of the negative asymmetric counter-ion. USAMMENFASSUNG:Es wird eine neue asymmetrische Synthese von Polymeren beschrieben, die aus Mononeren ohne asymmetrische C-Atome erhalten werdsn.-41s ungesattigte cyclische Verbindung konnte Benzofuran durch effnung und Poly-.ierisation der Dopprlbindung des Furanringes in Gegenwart von asymmetrischen katioiischen Katalysatoren in Polymere uberfuhrt werdel;, die eine hohe optische Aktivitat besitsen. Die Rotationsdispersionskurve zeigt ein Maximum bei 303 my ([MI = -800). I n diesen Pdynieren enthalt jede Monomereinheit zwei C-Atome in der Kette, dieauch in unmittelbarer Umgebung betrachtetasymmetrisch sind.Die optisch aktiven Polybenzofurane enthalten praktisch keine aus dem Katalysator stammenden asymmetrischen Endgruppen. Die asymmetrische Synthese kann daher auf die orientierende Wirkung des negativ asymmetrischen Gegenions zuriickgefiihrt werden.

Asymmetric Anionic Oligomerization of N-Substituted Citraconimide with the Chiral Ligand-Organometal Complex

“…The polymerization of RCI needed initiator concentration of 10 mo]% of the RCI to obtain enough yield. For the radical polymerization of RCI, yields were much lower than those for anionic polymerizations (run 18,19). Mn and polydispersity (MwfMn) of poly(NMI) were 500 and 1.3, respectively, the same as by anionic polymerization.…”

Asymmetric Polymerizations ofN‐Substituted Maleimides

“…Benzofuran was polymerized with AlEtCl 2 or AlCl 3 in the presence of optically active co-catalysts such as (S)-phenylalanine, 10-camphorsulfonic acid, and brucine to obtain optically active polymers with specific rotation [a] D of þ 13.1 to À33.1 in AlEtCl 2 systems and þ56.7 as the highest value in AlCl 3 systems [6][7][8][9][10]. Natta, Farina, and coworkers presented the first successful examples of asymmetric homopolymerization of a cyclic olefin without a C 2 axis of symmetry.…”

Main‐Chain Chirality and Optical Activity in Polymers Consisting of CC Chains

“…The existence of this type of structure has been verified particularly for the case of two different substituents (30b). [13,161 For clear representation of the stereochemical situation, one can also put the structural units of 27-30 (Fig. 8) into a ring structure.…”