The reaction of benzene-1,2-diol with various propargylic carbonates in the presence of a palladium catalyst and various chiral ligands afforded the corresponding 2-alkylidene-3-alkyl-2,3-dihydrobenzodioxins in quite good yields and enantioselectivities of up to 97%. The highest enantiomeric excesses were obtained using atropoisomeric diphosphanes as the chiral ligands; when Diop, BDPP and other ligands gave quite low enantioselectivities.
Axial-to-Central Chirality Transfer for Construction of Quaternary Stereocenters via Dearomatization of BINOLs
作者:Xiao-Long Min、Xu-Ran Xu、Ying He
DOI:10.1021/acs.orglett.9b03558
日期:2019.11.15
All-carbonquaternary stereocenters are versatile building blocks, and their asymmetric construction has attracted much attention. Herein, we disclose an axial-to-central chirality transfer strategy for the synthesis of chiralquaternary stereocenters via dearomatization of (S)-BINOLs. The reaction proceeded smoothly with a wide range of propargyl carbonates to afford chiral spiro-compounds in high
Palladium-Catalyzed Synthesis of 2,3-Dihydro-2-ylidene-1,4-benzodioxins
作者:Jean-Robert Labrosse、Paul Lhoste、Denis Sinou
DOI:10.1021/jo0103625
日期:2001.10.1
4-benzodioxins. The reaction is suggested to proceed by the formation of a (sigma-allenyl)palladium complex, followed by the intermolecular attack of the phenoxideion on this complex to generate a new (sigma-allyl)palladium complex in equilibrium with the corresponding (eta(3)-allyl)palladium complex. Intramolecular attack of the phenoxideion afforded the corresponding benzodioxan compound. This last