Bi(OAc)₃/Chiral Phosphoric Acid-Catalyzed Enantioselective 1,2- and Formal 1,4-Allylation Reaction of β,γ-Unsaturated α-Ketoesters

Abstract

A highly efficient asymmetric 1,2-allylation reaction of β,γ-unsaturated α-ketoesters was realized by using a Bi­(OAc)3/chiral phosphoric acid catalyst system under mild conditions. Meanwhile, using this combined strategy of enantioselective 1,2-allylation and subsequent anionic oxy-Cope rearrangement, the asymmetric formal 1,4-allylation reaction was achieved by a one-pot process. These reactions offer rapid access to an array of homoallylic tertiary alcohols and γ-allyl-α-ketoesters with good yields and excellent enantioselectivities. Density functional theory calculations were conducted to interpret the high enantioselectivity.

Recent Advances in Asymmetric Catalysis Using p‐Block Elements

“…The combination of Bi(OAc) 3 / (S)‐ L*3 c CPA for enantioselective transformations has also been extended to α‐ketoesters 97 (Scheme 23a) [34] . Reaction occurred at the keto group in the absence of KHMDS (potassium bis(trimethylsilyl)amide) but, when KHMDS was added, the formation of a highly enantioenriched 1,4‐allylation product 99 was obtained through an anionic oxy‐Cope rearrangement.…”

Recent Advances in Asymmetric Catalysis Using p‐Block Elements

“…The combination of Bi(OAc) 3 /(S)-L*3 c CPA for enantioselective transformations has also been extended to αketoesters 97 (Scheme 23a). [34] Reaction occurred at the keto group in the absence of KHMDS (potassium bis(trimethylsilyl)amide) but, when KHMDS was added, the formation of a highly enantioenriched 1,4-allylation product 99 was obtained through an anionic oxy-Cope rearrangement. A one-pot synthetic route accessed either tertiary homoallylic alcohols 98 or γ-allyl-α-ketoesters 99 with both high enantioselectivity (98 % ee), and in good to excellent yields (up to 99 % and 75 % yields, respectively).…”

Further developments of β,γ-unsaturated α-ketoesters as versatile synthons in asymmetric catalysis

“…It is noteworthy that this catalytic system could be further expanded to the asymmetry vinylation of α -ketoesters, isatins, and imines. Recently, the Li group revealed that Bi(OAc) 3 /chiral phosphoric acid catalyst system also showed high catalytic and stereocontrolling abilities in this kind of asymmetric 1,2-allylation reaction of allylboronic acid pinacol esters to β,γ -unsaturated α -ketoesters ( Liu et al., 2021 ). In addition, the Johnson group completed a three-component reductive coupling reaction between β,γ -unsaturated α -ketoesters, dimethyl phosphite and aldehydes ( scheme 6 B) ( Horwitz et al., 2016 ).…”