Solvent vs. counterion acceleration of enantioselective carbo and hetero Diels–Alder reactions

Abstract

The influence of solvents (CH₂Cl₂ and CH₃NO₂) vs. non-coordinating counterions (OTf and SbF₆; Tf = CF₃SO₂) on the catalytic properties of CuX₂–bisdihydrooxazoles in carbo and hetero Diels–Alder reactions has been studied. It has been observed that the use of CH₃NO₂ as the solvent enhances the reactivity of the Cu(OTf )₂–bisdihydrooxazole catalyst compared with the reactivity of CuX₂–bisdihydrooxazole in CH₂Cl₂ in these reactions. The use of CH₃NO₂ as the solvent in the carbo Diels–Alder reaction gives an 87% yield of the Diels–Alder adduct with 96% enantiomeric excess (ee), while in the hetero Diels–Alder reaction 98% yield and 97% ee is found under similar reaction conditions.

References

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