Synthesis of Polysubstituted Furans Based on a Stepwise Sonogashira Coupling of (Z)-3-Iodoalk-2-en-1-ols with Terminal Propargylic Alcohols and Subsequent Au(I)- or Pd(II)-Catalyzed Cyclization−Aromatization via Elimination of H<sub>2</sub>O
作者:Xiaobing Zhang、Zhan Lu、Chunling Fu、Shengming Ma
DOI:10.1021/jo100146p
日期:2010.4.16
Recently, we have developed highly regio- and stereoselective carbometalation of 2-alkynols and 2,3-allenols. The organometallacyclic intermediates may be trapped with 12 to afford 3-iodoalk-2-en-1-ols. These 3-iodoalk-2-en-1-ols may readily undergo the Sonogashira coupling with terminal propargyl alcohols to form 4-alkyn-2-ene-1,6-diols. Subsequent cycloisomerization in DMA or CH2Cl2 with Au(PPh3)Cl and AgOTf as the catalyst would afford polysubstituted 2-(1-alkenyl)furans; with PdCl2 as the catalyst and the reaction in DMA in the presence of allylic bromides, the same substrates afforded polysubstituted 2-( 1,4-alkadienyl)furans. In both types of catalyzed cyclization reactions, the elimination of H2O promoted the aromatization to form the furan ring. Different alkyl or aryl groups could be introduced into different positions of furans due to the substituent-loading capability of 3-iodoalkenols and diversity of the terminal propargyl alcohols and allylic bromides.
Synthesis of highly substituted allylic alcohols by a regio- and stereo-defined CuCl-mediated carbometallation reaction of 3-aryl-substituted secondary propargylic alcohols with Grignard reagents
作者:Xiaobing Zhang、Zhan Lu、Chunling Fu、Shengming Ma
DOI:10.1039/b903769a
日期:——
A highly regio- and stereoselective CuCl-mediated carbometallation reaction of 3-aryl-substituted secondary propargylicalcohols with alkyl, aryl, vinyl or allyl Grignard reagents for the synthesis of fully-substituted allylic alcohols was developed. The R2group from the Grignard reagent was successfully introduced to the 2-position of the propargylicalcohols due to the chelation of metal atom with