Enantioselective intermolecular cross Rauhut–Currier reactions of activated alkenes with acrolein

Abstract

The enantioselective intermolecular cross Rauhut-Currier reaction of acrolein with active olefins has been a long-standing challenge because of the competitive MBH reaction and polymerization. Herein a highly enantioselective intermolecular cross Rauhut-Currier reaction of acrolein with 3-acyl acrylates and 2-ene-1,4-diones, which is enabled by newly designed Peng-Phos catalysts. This method is scalable and highly enantioselective (up to 96% ee). Several transformations of the R-C products are carried out to showcase the synthetic utility.

Phosphine‐Catalyzed Asymmetric Umpolung Addition of Trifluoromethyl Ketimines to Morita–Baylis–Hillman Carbonates

“…[6] Very recently, Deng and co-workers successfully applied this umpolung strategy to the synthesis of optically active trifluoromethyl amines, with a chiral tertiary stereocenter, from readily available trifluoromethyl ketimines (1) and enals by the employing a chiral phase-transfer catalyst (PTC; Scheme 1 b). Inspired by Dengs work and our continual interest in asymmetric phosphine catalysis, [7,8] we envisaged that the Morita-Baylis-Hillman (MBH) carbonates 2, another very readily available and widely used compounds in organocatalytic reactions, [9] would generate the chiral quaternary phosphonium salts 3 in the presence of chiral phosphine catalyst (Scheme 1 c). Subsequent S N 2' reaction with the in situ generated 2-azaallyl anions 4 would deliver the corresponding enantioenriched trifloromethyl amines 5 with a chiral tertiary stereocenter.…”

Phosphine‐Catalyzed Enantioselective Dearomative [3+2]‐Cycloaddition of 3‐Nitroindoles and 2‐Nitrobenzofurans

“…[11][12][13] However, to the best of our knowledge,p hosphine catalytic asymmetric dearomative cycloaddition of 3-nitroindoles or 2-nitrobenzofurans has not been realized so far. This may be attributed to:1)the high energetic barrier in dearomative cycloaddition; [14] 2) regioselectivity outcome of the cycloaddition;a nd 3) control of diastereo-and enantioselectivities.W ith regard to the high importance of chiral indolines and benzodihydrofurans ( Figure 1) [15] and in continuation of our research program on asymmetric phosphine catalysis, [16] we became interest in the phosphine-catalyzed asymmetric dearomative cycloaddition of electron-deficient heteroarenes such as 3-nitroindoles and 2-nitrobenzofurans.W ee nvisioned that zwitterionic intermediate (A or B), generated from the addition of phosphine to allenoate 2,m ight react with 3-nitroindoles 1 through consecutive conjugate addition-a-o rg-addition, thereby leading to dearomative cycloaddition products (Scheme 2). Herein, we present the first example of phosphine-catalyzed asymmetric dearomative [3+ +2]-cycloaddition of 3-nitroindoles and 2-nitrobenzofurans with allenoates and MBH carbonates,r espectively,f or highly enantioselective synthesis of chiral indolines and benzodihydrofurans (Scheme 1g).…”

Phosphine‐Catalyzed Difunctionalization of β‐Fluoroalkyl α,β‐Enones: A Direct Approach to β‐Amino α‐Diazo Carbonyl Compounds

“…During our continuous efforts for developing phosphinecatalyzed [6,7] diverse transformations, [8] we envisaged that the phosphazide zwitterion intermediate might be competitively trapped with electrophiles,s uch as enones.T his could be achieved by slowing down the generation of the iminophosphorane,involving an intramolecular nucleophilic addition to generate the key triazole intermediate,leading to subsequent fragmentation to the b-amino a-diazo carbonyl compounds.If this hypothesis succeeds,w em ay open an ew window for transformations of azide into synthetic useful compounds with the use of phosphine catalyst. Herein we reported the first enantioselective phosphine-catalyzed difunctionalization of alkene by b-fluoroalkylated a,b-enone with TMSN 3 , furnishing af acile access to fluoroalkylated b-amino a-diazo carbonyl compounds (Scheme 1d).…”