Remarkable Effect of Silyl Groups on Asymmetric Induction in a Conjugate Addition Reaction with O-Methylnorephedrine-Based N-Silylamidocuprates

• Published in: Journal of the American Chemical Society Vol. 127; no. 5; pp. 1372 - 1373
• Main Authors: Bertz, Steven H, Ogle, Craig A, Rastogi, Abhinav
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 09.02.2005; Amer Chemical Soc
• Subjects: Chemical reactivity; Chemistry; Chemistry, Multidisciplinary; Exact sciences and technology; Organic chemistry; Physical Sciences; Reactivity and mechanisms; Science & Technology; CHIRAL P,N LIGANDS; ENONES; REAGENTS; COPPER CHEMISTRY; DIETHYLZINC; Substituent effect; Chiral auxiliary; Catalytic reaction; Lithium Organic compounds; Enantioselectivity; Copper Organic compounds; Steric effect; Homogeneous catalysis; Addition reaction; Experimental study; Asymmetric induction
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0455805

Scalemic N-silylamidocuprates, prepared from O-methylnorephedrine in a two-flask procedure, are exceedingly reactive and give excellent enantiomeric excesses with chalcone, a classic substrate for studies of organocuprate conjugate addition. For example, the butyl N-diphenylmethylsilylamidocuprate (T = Bu) affords a 99.2% ee (99% yield) of (S)-3-butyl-1,3-diphenyl-1-propanone. The remarkably high yields with this and other silyl ligands are attributed to the extraordinary activating effect of a β-silicon atom on organocuprate reactions. The high ee is a consequence of the larger size of the silyl ligands compared to that of the unsubstituted or methyl-substituted analogues.