PdCl<sub>2</sub>-Catalyzed Efficient Transformation of Propargylic Amines to (<i>E</i>)-α-Chloroalkylidene-β-lactams
作者:Shengming Ma、Bin Wu、Xuefeng Jiang
DOI:10.1021/jo0480996
日期:2005.4.1
The PdCl2-catalyzed cyclocarbonylation reaction of propargylic amines with CuCl2 and benzoquinone afforded (E)-alpha-chloroalkylidene-beta-lactams in moderate to good yields. The formation of the corresponding Z-isomers or five-membered products was not observed. The reaction of the readily available optically active propargylic amines provides a convenient synthesis of the corresponding (E)-alpha-chloroalkylidene-beta-lactams with high ee values. The structure and the stereochemistry of the products were established by the X-ray single-crystal diffraction study of (E)-6d and (E)-6e, which indicates that the stereoselectivity in this reaction is different from what was observed with propargylic alcohols. A rationale for this reaction was proposed.
Palladium-Catalyzed Construction of Polycyclic Heterocycles by an Alkyne Insertion and Direct Arylation Cascade
Cascade cyclization of bromoenynes bearing an aryl group with catalytic amounts of palladium(II) acetate and cesium carbonate led to the direct construction of tri- or tetracyclic heterocycles. Direct arylation of a pyrrole, furan or thiophene ring in the cascade reaction affords the corresponding fused heteroarenes in moderate to good yields. tandem reaction - palladium - polycycles - fused-ring systems