posted on 2017-02-22, 00:00authored byTakeo Sakai, Junpei Matsuoka, Masayuki Shintai, Yuji Mori
Rotamers
around the CAr–O bond were disclosed
in 3,3′-disubstituted BINOL esters by NMR spectroscopy. A bulky
R1 group increased the rotational barrier. The pivalate
showed two rotamers at 2 °C, and broad signals were observed
close to room temperature when R2 = Ph. The highest rotational
barrier was recorded for the (tetracyanocyclopentadienyl)carboxylate,
and C–O rotamers were present at room temperature. DFT calculations
indicated the presence of repulsion between R1 and R2 during rotation of the CAr–O bond.