The Newman-Kwart rearrangement
(NKR, 1→2)) was the last in a series of related
rearrangements, in which aryl groups migrate intramolecularly
between nonadjacent atoms, and that
were discovered and developed in the early to mid parts
of last century. The Schönberg rearrangement8 is the
most similar and involves 1,3-migration of an aryl group
from oxygen to sulfur (3→4, Scheme 2) in a diarylthioncarbonate.
The Chapman rearrangement9 involves analogous
migration but to nitrogen (5→6).