Enantioselective Radical Type, 1,2-Oxytrifluoromethylation of Olefins Catalyzed by Chiral Vanadyl Complexes: Importance of Noncovalent Interactions

Chien Tien Chen, Yu Cheng Su, Chia Hao Lu, Chien I. Lien, Shiang Fu Hung, Chan Wei Hsu, Rachit Agarwal, Ramuasagar Modala, Hung Min Tseng, Pin Xuan Tseng, Ryoma Fujii, Kyohei Kawashima, Seiji Mori

Research output: Contribution to journalArticlepeer-review

Abstract

Asymmetric three-component 1,2-oxytrifluoromethylations of styrenes were explored by using N-oxyphthalimide (NOPI) as the resulting benzylic radical anchor after cross-coupling by a CF3 radical under the catalyses of chiral N-salicylidene-derived oxovanadium(V) complexes. Among the 15 different solvents and 15 different catalysts examined, the best scenarios were in i-PrOH with C3-tert-butyl or C3-fluoro-/2,5-dimethylphenyl-substituted vanadyl catalysts that led to the corresponding complementary S and R products in up to 88% yields and 87/86% ees, respectively, with further enrichment to at least 94% ee after a single recrystallization. The ccontrol α-(2-phenylcyclopropyl)styrene was tested to prove the asymmetric event involving the benzylic radical species. DFT computations showed that the SOMO of the benzylic radical is placed in a way to orient the CF3CH2 group away from the tert-butyl group in the salicylidene-l-tert-butylglycinate template by interacting with the N-oxygen atom of NOPI bound to the vanadium center with a bimolecular homolytic substitution (SH2) type mechanism. The enantioselectivity profile was dominated by several noncovalent interactions between the intermediary vanadium(NOPI) complex and the resulting benzylic radical.

Original languageEnglish
Pages (from-to)7160-7175
Number of pages16
JournalACS Catalysis
Volume11
Issue number12
DOIs
Publication statusPublished - Jun 18 2021
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)

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