Rotational Behavior about the N3-Pyridyl Bond in 3-(Pyridin-2-yl)quinazolin-4-one and 4-Thione Derivatives.

The rotational barriers about the N3-(2-pyridyl) bond in 2- iso -propyl-3-(pyridin-2-yl)quinazolin-4-one and the thione analogue were evaluated though VT-NMR measurement of a diastereotopic iso -propyl group followed by a line-shape simulation. In 3-(pyridin-2-yl)quinazoline-4-thione bearing a chiral center as the C2 substituent, the formation of dynamic diastereomers was detected by NMR. The rotational pathway about the N3-(2-pyridyl) bond and the stereochemistries of dynamic diastereomers were revealed through a computational study.