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.
The asymmetric addition of lithium acetylides to carbonylcompounds in the presence of a chiral lithium binaphtholate catalyst was developed. A procedure involving the slow addition of carbonylcompounds to lithium acetylides improved the enantioselectivity. This reaction afforded diverse chiral secondary and tertiary propargylic alcohols in high yields and with good to high enantioselectivities.
Highly Enantioselective Phenylacetylene Additions to Ketones Catalyzed by (<i>S</i>)-BINOL−Ti Complex
作者:Yifeng Zhou、Rui Wang、Zhaoqing Xu、Wenjin Yan、Lei Liu、Yongfeng Kang、Zhijian Han
DOI:10.1021/ol0485621
日期:2004.11.1
Ti(O(i)Pr)(4) is an effective chiral catalyst for the catalytic asymmetricaddition of alkynylzinc to unactivated simple ketones. Good to excellent enantioselectivities were achieved. No previous case has been reported successfully using BINOL to catalyze the addition of phenylacetylene to unactivated ketones, and thus the utility of BINOL in asymmetric catalysis is expanded.
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.