Synthesis and Properties of a Novel Pyridineoxazoline Containing Optically Active Helical Polymer as a Catalyst Ligand for Asymmetric Diels–Alder Reaction |
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| Authors: | Heng Wang Na Li Jie Zhang Xinhua Wan |
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| Institution: | Beijing National Laboratory for Molecular Sciences, Key Laboratory of Polymer Chemistry and Physics of MOE, Center for Soft Matter Science and Engineering, College of Chemistry and Molecular Engineering, Beijing, China |
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| Abstract: | A novel pyridineoxazoline (PyOx) containing helical polymer, poly{(–)‐(S)‐4‐tert‐butyl‐2‐5‐(4‐tert‐butylphenyl)‐3‐vinylpyridin‐2‐yl]‐oxazoline} ( PA ), was designed and synthesized to approach the effect of chain conformation on the catalytic property. Its complex with Cu(OTf)2, i.e., Cu(II)-PA , was employed to catalyze the homogeneous Diels–Alder (D–A) reaction of alkenoyl pyridine N‐oxides with cyclopentadiene in tetrahydrofuran. Compared with the previously reported copper complex, Cu(II)-P1 (RSC Advances, 2015, 5 , 2882), which was derived from a nonhelical poly(–)‐(S)‐4‐tert‐butyl‐2‐(3‐vinylpyridin‐2‐yl)‐oxazoline], Cu(II)-PA exhibited a remarkably enhanced enantioselectivity and reaction rate. However, its enantioselectivity was lower than the Cu(II) complex of (–)‐(S)‐4‐tert‐butyl‐2‐5‐(4‐tert‐butylphenyl)‐3‐vinylpyridin‐2‐yl]‐oxazoline ( Cu(II)-A ), a low molar mass model compound. Chirality 27:523–531, 2015. © 2015 Wiley Periodicals, Inc. |
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| Keywords: | radical polymerization chiral induction enantiomer excess optical active helical polymer– copper(II) complex polymer based catalysis |
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