Highly enantioselective tandem cyclopropanation/Wittig reaction of α,β-unsaturated aldehydes with arsonium ylides catalyzed by recyclable dendritic catalyst

A novel tandem cyclopropanation/Wittig reaction of α,β-unsaturated aldehydes with arsonium ylides using a chiral 2-trimethylsilanyloxy-methyl-pyrrolidine-based dendritic catalyst is described. Good yields (up to 86%), and high diastereoselectivities (up to dr = 99:1) and enantioselectivities (up to 99% ee) were obtained under simple and mild reaction conditions. The catalyst can be recycled without any loss in activity.

Figure optionsDownload as PowerPoint slide

(E)-3-((1R,2R,3R)-2-Benzoyl-3-phenylcyclopropyl)-1-phenylprop-2-en-1-oneC25H20O2Ee = 98%[α]D25=-36.0 (c 1.53, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1R,2R,3R)

(E)-3-((1R,2R,3R)-2-(4-Fluorobenzoyl)-3-phenylcyclopropyl)-1-(4-fluorophenylprop)-2-en-1-oneC25H18F2O2Ee = 99%[α]D25=+7.7 (c 0.88, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1R,2R,3R)

(E)-3-((1R,2R,3R)-2-(4-Chlorobenzoyl)-3-phenylcyclopropyl)-1-(4-chlorophenylprop)-2-en-1-oneC25H18Cl2O2Ee = 99%[α]D25=-21.3 (c 0.83, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1R,2R,3R)

(E)-3-((1R,2R,3R)-2-(4-Bromobenzoyl)-3-phenylcyclopropyl)-1-(4-bromophenylprop)-2-en-1-oneC25H18Br2O2Ee = 93%[α]D25=-31.2 (c 0.74, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1R,2R,3R)

(E)-3-((1R,2R,3R)-2-(4-Methylbenzoyl)-3-phenylcyclopropyl)-1-(4-methylphenylprop)-2-en-1-oneC27H24O2Ee = 99%[α]D25=-10.2 (c 0.61, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1R,2R,3R)

(E)-3-((1R,2R,3R)-2-(4-Methoxyllbenzoyl)-3-phenylcyclopropyl)-1-(4-methoxylphenylprop)-2-en-1-oneC27H24O4Ee = 94%[α]D25=55.2 (c 0.32, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1R,2R,3R)

(E)-3-((1R,2R,3R)-2-Benzoyl-3-(4-methoxylphenyl)-cyclopropyl)-1-phenylprop-2-en-1-oneC26H22O3Ee = 92%[α]D25=-10.2 (c 0.74, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1R,2R,3R)

(E)-3-((1R,2R,3R)-2-(4-Bromobenzoyl)-3-(4-methoxylphenyl)-cyclopropyl)-1-(4-bromophenylprop)-2-en-1-oneC26H20Br2O3Ee = 87%[α]D25=-29.7 (c 1.00, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1R,2R,3R)

(E)-3-((1R,2R,3R)-2-Benzoyl-3-methyl-cyclopropyl)-1-phenylprop-2-en-1-oneC20H18O2Ee = 71%[α]D25=-22.2 (c 0.38, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1R,2R,3R)

(E)-3-((1R,2R,3R)-2-Benzoyl-3-propyl-cyclopropyl)-1-phenylprop-2-en-1-oneC22H22O2Ee = 80%[α]D25=-33.2 (c 0.34, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1R,2R,3R)