Mild and Expedient Asymmetric Reductions of α,β-Unsaturated Alkenyl and Alkynyl Ketones by TarB-NO<sub>2</sub> and Mechanistic Investigations of Ketone Reduction
作者:Scott Eagon、Cassandra DeLieto、William J. McDonald、Dustin Haddenham、Jaime Saavedra、Jinsoo Kim、Bakthan Singaram
DOI:10.1021/jo101530f
日期:2010.11.19
yields up to 99%. In the case of α,β-unsaturated alkenyl ketones, α-substituted cycloalkenones were reduced with up to 99% ee, while more substituted and acyclic derivatives exhibited lower induction. For α,β-ynones, it was found that highly branched aliphatic ynones were reduced with optimal induction up to 90% ee, while reduction of aromatic and linear aliphatic derivatives resulted in more modest enantioselectivity
Reductive cleavages of homochiral acetalsusing Lewis acid-hydride systems and of alkynyl acetalsusingorganoaluminumreagents are described. Stereochemical outcomes are found to be the opposite compared with our previous results on the aluminum hydride reduction of the acetal.
Niwa, Seiji; Soai, Kenso, Journal of the Chemical Society. Perkin transactions I, 1990, # 4, p. 937 - 943
作者:Niwa, Seiji、Soai, Kenso
DOI:——
日期:——
Studies on Pd(II)-Catalyzed Synthesis of (<i>Z</i>)-α-Haloalkylidene-β-lactones from Cyclocarbonylation of 2-Alkynols and the Subsequent Coupling Reactions
作者:Shengming Ma、Bin Wu、Xuefeng Jiang、Shimin Zhao
DOI:10.1021/jo0480038
日期:2005.4.1
A good regio- and stereoselectivity was observed for the PdCl2-catalyzed cyclocarbonylation of 2-alkynols with CuCl2 affording (Z)-alpha-chloroalkylidene-beta-lactons. The highly optically active (Z)-alpha-chloroalkylidene-beta-lactones could be easily prepared from the readily available optically active propargylic alcohols. The Pd(II)-catalyzed cyclocarbonylation of 2-alkynols with CuBr2 was also studied. Although the yields of (Z)-alpha-bromoalkylidene-beta-lactones were low, due to the relatively higher activity of the C-Br bond, the coupling reactions of (Z)-alpha-bromoalkylidene-beta-lactones were quite smooth to afford the corresponding products in high yields. A rationale for this reaction is discussed.
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.