Stereoselective Synthesis of Cyclic Ethers Using Vinylogous Sulfonates as Radical Acceptors: Effect of <i>E</i>/<i>Z</i> Geometry and Temperature on Diastereoselectivity
作者:P. Andrew Evans、Thara Manangan
DOI:10.1021/jo991970b
日期:2000.7.1
function of the acyl radicalgeometry (sp2) and high inversion barrier (29 kcal/mol) as compared to the alkyl (1 kcal/mol) and vinyl (2.9 kcal/mol) radicals. This is consistent with the acyl radical cyclization having an earlier transition state than the corresponding alkyl and vinyl radicals. The modest diastereoselectivity can be improved dramatically using the Z-vinylogous sulfonate (> or =34:1; R =