Cage-shaped borate esters with enhanced Lewis acidity and catalytic activity.
[structure: see text] A cage shape causes high Lewis acidity and catalytic activity on boron. Borate esters that have cage-shaped ligands have accessible LUMO with lower eigenvalues than normal open-shaped borate esters. A large dihedral angle at C-O-B-O in cage-shaped borate esters induces less overlap between p-orbitals on O and B. The hetero-Diels-Alder reaction is effectively catalyzed by the cage-shaped borate, although the open-shaped borate does not act as a catalyst.
Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan. yasuda@chem.eng.osaka-u.ac.jp
Makoto
M
Yasuda
Sachiko
S
Yoshioka
Satoshi
S
Yamasaki
Toshio
T
Somyo
Kouji
K
Chiba
Akio
A
Baba