Asymmetric Synthesis of Functionalized Cyclopropanes via β-Lithiation-Cyclization of N-Monosubstituted 3-(Phenylthio)-2-propanamides

Article abstract of DOI:10.1021/ja00229a038

The reaction of N-<(1R,2S,3R,4S)-2-hydroxy-1,7,7-trimethylbicyclohept-3-yl>-3-(phenylthio)-2-<(phenylthio)methyl>propanamide with 4 equiv of n-BuLi gives exclusively trans cyclopropanes in 94 percent yield (ratio of diastereomers 1:3).The use of the triisopropylsilyl ether of the amide led to high diastereoselectivity (ratio 1:11) in this cyclopropanation.The absolute configuration of the resulting diastereomeric cyclopropane was determined by X-ray crystallography.The β-lithiation and subsequent alkylation of the cyclopropanes provided a wide variety of optically pure cyclopropane derivatives.