The reactions of o-lithiated O-aryl N,N-diethylcarbamates
with different C−N multiple bond electrophiles have been
thoroughly studied. A 1,5-O → N carbamoyl shift, a new variation
of the anionic Fries-type rearrangement, takes place when nitriles,
imines, or alkylcarbodiimides are employed. In these cases, the
carbamoyl group plays a dual role as a directing group, building up
a variety of functional groups through the 1,5-O → N carbamoyl
migration. On the other hand, the use of iso(thio)cyanates and
arylcarbodiimides led to non-rearranged o-functionalized Oarylcarbamates.
This reactivity was further computationally
explored, and the governing factor could be traced back to the
relative basicity of the alternative products (migrated vs nonmigrated
substrates). This exploration also provided interesting insights about the degree of complexation of the lithium cations onto
these substrates. A new access to useful 2-hydroxybenzophenone derivatives has also been developed.
