Copper-catalyzed asymmetric addition of diethylzinc to Boc-protected imines

A new class of substrates has been tested in the addition of Et2Zn, catalyzed by copper and phosphoramidite, providing the expected α branched protected amine in quantitative conversion, good yield and excellent enantioselectivity up to 97%.

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(S)-tert-Butyl 1-phenylpropylcarbamateC14H21NO2Ee = 93%[α]D20=-53.5 (c 1.025, CHCl3)Source of chirality: asymmetric synthesis

(S)-tert-Butyl 1-p-tolylpropylcarbamateC15H23NO2Ee = 94%[α]D20=-60.7 (c 1.02, CHCl3)Source of chirality: asymmetric synthesis

(S)-tert-Butyl 1-(4-(trifluoromethyl)phenyl)propylcarbamateC15H20F3NO2Ee = 96%[α]D20=-41.5 (c 0.99, CHCl3)Source of chirality: asymmetric synthesis

(S)-tert-Butyl 1-(4-methoxyphenyl)propylcarbamateC15H23NO3Ee = 93%[α]D20=-70.7 (c 0.995, CHCl3)Source of chirality: asymmetric synthesis

(S)-tert-Butyl 1-(benzo[d][1,3]dioxol-5-yl)propylcarbamateC15H23NO3Ee = 94%[α]D20=-63.1 (c 0.995, CHCl3)Source of chirality: asymmetric synthesis

(S)-tert-Butyl 1-(naphthalen-2-yl)propylcarbamateC18H23NO2Ee = 90%[α]D20=-58.1 (c 1.03, CHCl3)Source of chirality: asymmetric synthesis

(S)-tert-Butyl 1-(furan-2-yl)propylcarbamateC12H19NO3Ee = 97%[α]D20=-99.8 (c 0.995, CHCl3)Source of chirality: asymmetric synthesis