Acceleration effect of Lewis acid in allylboration of aldehydes: catalytic, regiospecific, diastereospecific, and enantioselective synthesis of homoallyl alcohols.
The addition of pinacol allylboronic esters to aromatic and aliphatic aldehydes smoothly occurred at -78 degrees C in toluene in the presence of a catalytic amount of AlCl3 or Sc(OTf)3 (10 mol %) to give the corresponding homoallyl alcohols in high yields. The reactions proceeded regio- and diastereospecifically, yielding the isomerically pure syn- and anti-homoallyl alcohols from (Z)- and (E)-allylboronic esters, respectively. The protocol was also applied to enantioselective reactions by using a chiral Lewis acid catalyst.
Ishiyama
Tatsuo
T
Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan. ishiyama@org-mc.eng.hokudai.ac.jp
Ahiko
Taka-aki
TA
Miyaura
Norio
N