Lithium ynolates reacted with N-2-methoxyphenyl (OMP) aldimines to afford α,β-unsaturated amides in excellent E-selectivity via a retro-Mannich reaction of the 2:1 adducts (β-lactams), followed by cleavage of the β-lactam enolates.
β-Amino esters via the Reformatsky reaction: Restraining effects of the ortho-methoxyphenyl substituent
作者:James C. Adrian、Julia L. Barkin、Lamyaa Hassib
DOI:10.1016/s0040-4039(99)00248-8
日期:1999.3
β-Amino esters are, in most cases, the only products of the Reformatskyreaction in CH2Cl2 between (methoxycarbonyl)methyl zinc bromide (prepared in-situ) and imines prepared from either an aryl or alkyl aldehyde and o-anisdine (Scheme 2). Restraining properties of the ortho-methoxyphenyl group, which lead to sole formation of the β-amino ester, are ascribed to the inductive effect of the ortho-methoxy
Enantioselective Synthesis of Propargylamines through Zr-Catalyzed Addition of Mixed Alkynylzinc Reagents to Arylimines
作者:John F. Traverse、Amir H. Hoveyda、Marc L. Snapper
DOI:10.1021/ol035138b
日期:2003.9.1
[reaction: see text] Addition of mixed alkynylzinc reagents to various arylimines is catalyzed by chiral amino acid-based ligand 1 and Zr(Oi-Pr)(4).HOi-Pr to afford chiral propargylamines in up to 90% ee. Oxidative removal of the o-anisidyl group affords the free amine, which can then be acylated.
The cycloaddition of the N-2-methoxyphenyl aldimines with lithium ynolates was efficiently accelerated via chelation to give β-lactam enolates, which immediately reacted with one more equivalent of the imine to give β-lactams (2:1 adducts) in good yields, while N-4-methoxyphenyl imines were inert towards lithium ynolates.