Synthesis of cis,syndiotactic‑A‑alt-B Copolymers from Enantiomerically Pure Endo-2-Substituted-5,6-Norbornenes

• Published in: Journal of the American Chemical Society Vol. 139; no. 14; pp. 5043 - 5046
• Main Authors: Jang, Eun Sil, John, Jeremy M, Schrock, Richard R
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 12.04.2017; American Chemical Society (ACS)
• Subjects: Chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.7b01747

Cis,syndiotactic A-alt- B copolymers, where A and B are two enantiomerically pure endo-2-substituted-5,6-norbornenes with “opposite” chiralities of the endo-2-substituted-5,6-norbornene skeleton, can be prepared using Mo­(N-2,6-Me2C6H3)­(CHCMe2Ph)­(OHMT)­(pyrrolide) (1) as the initiator (OHMT = O-2,6-Mesityl2C6H3). Formation of a high percentage of A-alt- B dyads is proposed to rely on an inversion of chirality at the metal with each propagating step and a kinetically preferred diastereomeric relationship between a given chirality at the metal in propagating species and the chirality of the endo-2-substituted-5,6-norbornene skeleton. We also demonstrate that A-alt- B copolymers can be modified to give new variations which may not be accessible through direct copolymerization.