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.
Chiral Hetero- and Carbocyclic Compounds from the Asymmetric Hydrogenation of Cyclic Alkenes
作者:J. Johan Verendel、Jia-Qi Li、Xu Quan、Byron Peters、Taigang Zhou、Odd R. Gautun、Thavendran Govender、Pher G. Andersson
DOI:10.1002/chem.201104073
日期:2012.5.21
Several types of chiral hetero‐ and carbocycliccompounds have been synthesized by using the asymmetrichydrogenation of cyclicalkenes. N,P‐Ligated iridium catalysts reduced six‐membered cyclicalkenes with various substituents and heterofunctionality in good to excellent enantioselectivity, whereas the reduction of five‐membered cyclicalkenes was generally less selective, giving modest enantiomeric