由(R)-1,1'-bi-2-萘酚[(R)-BINOL],Ti(O- i -Pr)4,H 2 O和氯化锂生成的组合路易斯酸催化体系有效在温和条件下,催化Brassard's二烯与芳族醛的对映选择性乙烯基醇醛缩醛反应,可提供(Z)-δ-羟基-α,β-不饱和酯,收率高,对映选择性极好(90-99%ee)。基于一些控制实验,提出了路易斯酸-路易斯酸双功能工作模型用于催化过程。
the hetero-Diels–Alder (HDA) reaction of the Brassarddiene with aldehydes in the presence of a series of titanium(IV) tridentate Schiff-base complexes under mild conditions. The influence of the substituent of the chiral Schiff-base ligands on the enantioselectivities of the reaction was studied. It was found that ligand L13 is a highly enantioselective ligand for the Ti-catalyzed HDA reaction, affording
[reaction: see text] Hetero-Diels-Alder reactions of Brassard diene with aromatic aldehydes were carried out smoothly in the presence of titanium(IV) tridentate Schiffbasecomplexes to give the corresponding chiral delta-lactones in high enantioselectivities (up to 99% ee) under mild conditions.
A One-Step Synthesis of 2,3-Dihydro-4<i>H</i>-pyran-4-ones from 3-Ethoxy α,β-Unsaturated Lactones
作者:Jeffrey D. Winkler、Kyungsoo Oh
DOI:10.1021/ol050702z
日期:2005.6.1
[GRAPHICS]Addition of diverse nucleophiles to the unsaturated lactone 2 that results from hetero Diels-Alder reaction of Brassard's diene 1 with aldehydes leads to an efficient and general approach to the synthesis of 2,3-dihydro-4H-pyran-4-ones 3.
Koegl; de Bruin, Recueil des Travaux Chimiques des Pays-Bas, 1950, vol. 69, p. 729,741