Lactic acid derived aziridinyl alcohols as highly effective catalysts for asymmetric additions of an organozinc species to aldehydes

A straightforward synthetic route to a series of new catalysts bearing secondary hydroxyl and aziridine moieties as nucleophilic centers built on the chiral skeleton of (S)-(+)-lactic acid is described. All of the new compounds have been tested in the enantioselective addition of diethyl- and phenylethynylzinc to aryl and alkyl aldehydes, yielding the corresponding chiral alcohols in high chemical yields (up to 85%) and good ee’s of approximately 85%. The influence of the stereogenic center located at the aziridine subunit on the stereochemical outcome is also discussed.

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(S)-(+)-1-((R)-2-Methylaziridin-1-yl)-propan-2-olC6H13NOEe = 99%[α]Drt=+3.5 (c 1, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,R) (literature data)

(S)-(+)-1-(2,2-Dimethylaziridin-1-yl)-propan-2-olC7H15NOEe = 98%[α]Drt=+7.2 (c 1, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S) (literature data)

(S)-(−)-1-((R)-2-Isopropylaziridin-1-yl)-propan-2-olC8H17NOEe = 99 %[α]Drt=-12.7 (c 1, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,R) (literature data)

(S)-(+)-1-((S)-2-Isopropylaziridin-1-yl)-propan-2-olC8H17NOEe = 98%[α]Drt=+3.4 (c 1, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S) (literature data)