achieved. So far the most economic catalyst system was developed for the addition of terminal alkynes to aromatic aldehydes in terms of ligand loading and enantioselectivity. Moreover, ligand 7a in combination with Ti(O-i-Pr)4 was found to be effective in promoting the addition reaction of an alkynylzinc reagent to unactivated simple ketones under very mild conditions. The corresponding chiral tertiary propargylic
A chiral copper complex, generated from a C 2-symmetric bis(hydroxycamphorsulfonamide) ligand (8 mol%) and Cu(OTf)2, has been discovered to effect high enantioselectivities in the addition of alkynylzinc to a series of simple ketones. The alkynylation of a variety of aromatic and aliphatic ketones resulted in excellent yields and enantioselectivities (83-98% ee). Even when the loadings of the catalyst is 5 mol%, up to 94% ee was obtained.
Chiral lithium binaphtholate effectively catalyzed the enantioselectivealkynylation of ketones using lithium acetylide as an alkynylating agent. This is the first example of the catalytic enantioselective addition of lithium acetylide to carbonyl compounds without the aid of other metal sources.
Enantioselective alkynylation of aldehydes and ketones was accomplished using trimethoxysilylalkynes as alkynylating reagents and lithium 3,3′-diphenylbinaphtholate as a catalyst. Optically active propargylic alcohols were obtained in good to high chemical yields and enantioselectivities. Alkynylation of acetylpyridines afforded biologically active pyridyl propargylic alcohols in good enantioselectivities
Catalytic asymmetric addition of alkynylzinc reagents to ketones using polymer-supported chiral Schiff-base amino alcohols
作者:Chao Chen、Liang Hong、Bangzhi Zhang、Rui Wang
DOI:10.1016/j.tetasy.2007.11.040
日期:2008.2
Polymer-supported Schiff-base of optically active amino alcohols was used as chiralligands in the enantioselective addition of alkynylzinc to simple ketones. At a 10 mol % ligand loading, chiral propargylic alcohols with moderate to good ee values (up to 89%) were produced. The polymeric catalyst could be recycled many times and used for further reactions.