Highly efficient conjugate additions of diethylzinc to enones promoted by chiral aziridine alcohols and aziridine ethers

Chiral heteroorganic N-trityl aziridine alcohols and aziridine ethers have proven to be highly efficient catalysts in enantioselective conjugate diethylzinc additions to enones, namely chalcone and 2-cyclohexen-1-one providing the desired chiral adducts in high chemical yields (up to 95%) and with ee’s up to 93%. The change of the absolute configuration of the stereogenic center located at the aziridine moiety on the stereochemical outcome is also discussed.

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(S)-(−)-1-Triphenylmethyl-2-α-hydroxyethylaziridineC23H23NOEe = 99%[α]Drt = −2.7 (c 1, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S) for aziridine (literature data), nd for C-OH

(S)-(−)-1-Triphenylmethyl-2-α-hydroxybenzylaziridineC28H25NOEe = 98%[α]Drt = −2.9 (c 1, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S) for aziridine (literature data), nd for C-OH

(S)-(−)-1-Triphenylmethyl-2-α-hydroxy-3-methylpropylaziridineC25H27NOEe = 99%[α]Drt = −2.5 (c 1, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S) for aziridine (literature data), nd for C-OH

(R)-(+)-2-Methyl-1-(2-phenoxyethyl)aziridineC11H15NOEe = 99%[α]Drt = +4.0 (c 1, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R) (literature data)

(R)-(−)-1-(2-Phenoxyethyl)-2-(propan-2-yl)aziridineC13H19NOEe = 99%[α]Drt = −0.3 (c 1, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R) (literature data)

(R)-(−)-1-(2-Benzyloxyethyl)-2-(propan-2-yl)aziridineC14H21NOEe = 99%[α]Drt = −0.4 (c 1, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R) (literature data)

(R)-(−)-1-(2-(4-tert-Butyl)phenoxyethyl)-2-(propan-2-yl)aziridineC17H27NOEe = 99%[α]Drt = −0.9 (c 1, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R) (literature data)

(R)-(−)-1-(2-(4-Chloro)phenoxyethyl)-2-(propan-2-yl)aziridineC13H18ClNOEe = 99%[α]Drt = +5.4 (c 1, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R) (literature data)