Catalytic Ring Expansion of Vinyl Oxetanes: Asymmetric Synthesis of Dihydropyrans Using Chiral Counterion Catalysis
作者:Boying Guo、Gregg Schwarzwalder、Jon T. Njardarson
DOI:10.1002/anie.201201367
日期:2012.6.4
Acid Showdown! The first catalyticring expansion of vinyl oxetanes to 3,6‐dihydro‐2H‐pyrans is described. Copper(II) triflate emerged as the best catalyst for this new transformation, which has broad scope as demonstrated by the eighteen examples included. The symmetric vinyl oxetane substrate can be asymmetrically desymmetrized when using either chiral Lewis or Brønsted acids as catalysts.
One-Pot, Three-Component Synthesis of 4-Aryl-5,6-dihydropyran via Prins-Friedel-Crafts Reaction
作者:Anil Saikia、Udagandla Reddy
DOI:10.1055/s-0029-1219779
日期:2010.4
An efficient method for the synthesis of 4-aryldihydropyrans has been developed from the reaction of aldehydes or epoxides with homopropargylic alcohols in the presence of arenes promoted by borontrifluoride etherate.