Synthetic applications of lithiated N-Boc allylic amines as asymmetric homoenolate equivalents.
Lithiation of N-(Boc)-N-(p-methoxyphenyl) allylic amines in the presence of (-)-sparteine provides asymmetric homoenolate equivalents which react with electrophiles to provide highly enantioenriched enecarbamates. Acidic hydrolysis of the enecarbamates can provide the corresponding beta-substituted aldehydes. A synthetic sequence that involves a stereocontrolled intramolecular nitrone-olefin dipolar cycloaddition has been developed for the preparation of enantioenriched 2-formyl-4-phenyl-1-aminocyclopentanes from one beta-allyl-substituted aldehyde. Further manipulations allow access to an enantioenriched beta-lactam. In another synthetic sequence, transmetalation of the lithiated intermediates and reactions with aldehyde electrophiles can be controlled to afford highly enantioenriched anti homoaldol products. Use of an anti aldehyde homoaldol product as the chiral electrophile in an iterative reaction provides a double homoaldol product containing four stereogenic centers with high diastereoselectivity and enantioselectivity. Reaction pathways are proposed to account for the observed products.
Whisler
Marna C
MC
Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.
Beak
Peter
P
D000447:Aldehydes / Q000138:chemical synthesis; D000498:Allyl Compounds / Q000737:chemistry*; D000588:Amines / Q000737:chemistry*; D002219:Carbamates / Q000138:chemical synthesis*; D002384:Catalysis; D002625:Chemistry, Organic / Q000379:methods*; D003517:Cyclopentanes / Q000138:chemical synthesis; D007769:Lactams / Q000138:chemical synthesis; D008094:Lithium / Q000737:chemistry*; D015394:Molecular Structure; D013034:Sparteine / Q000737:chemistry; D013237:Stereoisomerism
D000447:Aldehydes; D000498:Allyl Compounds; D000588:Amines; D002219:Carbamates; D003517:Cyclopentanes; D007769:Lactams; D013034:Sparteine; D008094:Lithium