Limonene oxide derived aziridinyl alcohols as highly efficient catalysts for asymmetric additions of organozinc species to aldehydes

The facile synthesis of a series of novel catalysts bearing a tertiary hydroxyl group and an aziridine moiety as chelating centers constructed on the scaffold derived from limonene oxide is described. The newly prepared compounds have been tested for the enantioselective addition of diethylzinc and phenylethynylzinc to aryl and alkyl aldehydes, affording the corresponding chiral alcohols in very high chemical yields (up to 96%) and with excellent ee’s of ca. 95%.

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(−)-(1S,2S,4R)-2-((2S)-2-Phenylaziridinyl)-1-methyl-4-(1-methylethenyl)cyclohexanolC18H25NOEe = 99%[α]Drt=-14.8 (c 1, CHCl3)Source of chirality: Asymmetric synthesisAbsolute configuration: (1S,2S,4R) (literature data)

(+)-(1S,2S,4R)-2-((2S)-2-Methylaziridinyl)-1-methyl-4-(1-methylethenyl)cyclohexanolC13H22NOEe = 99%[α]Drt=+9.3 (c 1, CHCl3)Source of chirality: Asymmetric synthesisAbsolute configuration: (1S,2S,4R) (literature data)

(+)-(1S,2S,4R)-2-((2S)-2-Isopropylylaziridinyl)-1-methyl-4-(1-methylethenyl)cyclohexanolC15H27NOEe = 99%[α]Drt=+11.2 (c 1, CHCl3)Source of chirality: Asymmetric synthesisAbsolute configuration: (1S,2S,4R) (literature data)

(−)-(1S,2S,4R)-2-((2R)-2-Isopropylylaziridinyl)-1-methyl-4-(1-methylethenyl)cyclohexanolC15H27NOEe = 98%[α]Drt=-2.0 (c 1, CHCl3)Source of chirality: Asymmetric synthesisAbsolute configuration: (1S,2S,4R) (literature data)