Diethyl phosphite mediated reductive [1 + 4] annulation of α-ketoesters with α, β-unsaturated ketones and synthesis of polysubstituted 2,3-dihydrofurans

Synthesis of Polysubstituted 2,3-Dihydrofurans via P(NMe2)3- Mediated [1＋4] Annulation of 1,2-Dicarbonyl Compounds with α,β-Unsaturated Ketones

“…Although above encouraging progress has been made, the [1＋4] annulation reaction of acyclic 1,2-dicarbonyl compounds with α,β-unsaturated ketones has not yet been reported. Recently, He's group [12] reported a diethyl phosphite mediated reductive [1 ＋ 4] annulation of α-ketoesters with α,β-unsaturated ketones, leading to polysubstituted dihydrofurans (Scheme 1, c). Inspired by the previous work, [9][10][11][12] and as a continuation of our efforts to develop [1＋4] annulation reactions, we have further studied a P(NMe 2 ) 3 -mediated [1＋4] annulation reaction of acyclic 1,2-dicarbonyl compounds with α,β-unsaturated ketones based on the chemistry of Kukhtin-Ramirez adducts (Scheme 1, d).…”

Chiral Lewis Acid-Catalyzed Asymmetric Multicomponent Michael Reaction through [1,2]-Phospha-Brook Rearrangement

“…Very recently, we developed a Lewis acid-catalyzed enantioselective γ-protonation of α-alkynylketoamides and diarylphosphine oxides with the assistance of water (Scheme c), confirming that chiral N , N ′-dioxide/metal complexes are efficient catalysts to enable [1,2]-phospha-Brook rearrangement. Inspired by this work, we envisaged the possibility of an asymmetric multicomponent reaction of ketone and phosphite with a suitable Michael acceptor catalyzed by chiral Lewis acid. Herein, we reported the diastereo- and enantioselective multicomponent tandem Pudovik addition/[1,2]-phospha-Brook rearrangement/Michael reaction of isatins, phosphites, and 4-oxobutenoates under mild reaction conditions by taking advantage of the chiral N,N ′-dioxide/Sc III complex as the catalyst (Scheme d).…”