Highly enantioselective syntheses of anti homoaldol products by (-)-sparteine-mediated lithiation/transmetalation/substitution of N-Boc allylic amines.
[reaction: see text](-)-Sparteine-mediated lithiation/transmetalation/substitution of N-Boc allylic amines provides anti-configured homoaldol precursors in yields of 38-85% and enantiomeric ratios of 83:17-99:1. Subsequent O-protection and hydrolysis allows access to O-protected homoaldol adducts in good yields. The absolute configurations of the homoaldol products have been assigned by calculation of optical rotations and by X-ray crystallography of derivatives. A stereochemical course of reaction for the lithiation/transmetalation/substitution sequence is proposed.
Whisler
M C
MC
Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana 61801, USA.
Vaillancourt
L
L
Beak
P
P
D000588:Amines / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D007202:Indicators and Reagents; D008094:Lithium / Q000737:chemistry*; D008968:Molecular Conformation; D013034:Sparteine / Q000737:chemistry*; D013237:Stereoisomerism; D014025:Titanium / Q000737:chemistry
D000588:Amines; D007202:Indicators and Reagents; D013034:Sparteine; D008094:Lithium; D014025:Titanium