Palladium-Templated Regio- and Stereoselective Cyclization of 2'-Alkenyl 2-Alkynoates and Its Synthetic Applications
摘要:
2'-Alkenyl 2-alkynoates undergo facile stereoselective cyclization to alpha-(haloalkylidene)-gamma-butyrolactones upon treatment with a catalytic amount of palladium complex in the presence of CuX(2) and LiX. When an alkyl group is introduced to the 1'-position of the alkenyl group, unsubstituted 2-propynoates mainly give trans-beta, gamma-disubstituted gamma-lactones, and substituted 2-propynoates afford cis-beta,gamma-disubstituted gamma-lactones. Further elaborations of the halogen atoms and the synthesis of A-factor using this method are exemplified.
Palladium(II)-Catalyzed Asymmetric Cyclization of (<i>Z</i>)-4‘-Acetoxy-2‘-butenyl 2-Alkynoates. Role of Nitrogen-Containing Ligands in Palladium(II)-Mediated Reactions
作者:Qinghai Zhang、Xiyan Lu、Xiuling Han
DOI:10.1021/jo0105181
日期:2001.11.1
2'-bipyridine) catalyzed the cyclization of (Z)-4'-acetoxy-2'-butenyl 2-alkynoates (1) in acetic acid to afford the alpha-(Z)-acetoxyalkylidene-beta-vinyl-gamma-butyrolactones (2) with high efficiency and high stereoselectivity. The nitrogen-containing ligands, like halides, served to favor beta-heteroatom elimination over beta-hydride elimination in Pd(II)-mediated reactions. The generality of this
Palladium-Templated Regio- and Stereoselective Cyclization of 2'-Alkenyl 2-Alkynoates and Its Synthetic Applications
作者:Jianguo Ji、Chunming Zhang、Xiyan Lu
DOI:10.1021/jo00110a018
日期:1995.3
2'-Alkenyl 2-alkynoates undergo facile stereoselective cyclization to alpha-(haloalkylidene)-gamma-butyrolactones upon treatment with a catalytic amount of palladium complex in the presence of CuX(2) and LiX. When an alkyl group is introduced to the 1'-position of the alkenyl group, unsubstituted 2-propynoates mainly give trans-beta, gamma-disubstituted gamma-lactones, and substituted 2-propynoates afford cis-beta,gamma-disubstituted gamma-lactones. Further elaborations of the halogen atoms and the synthesis of A-factor using this method are exemplified.