We report the development
of ureas as sterically undemanding pro-ligands
for Pd catalysis.
N
-Arylureas outperform phosphine
ligands for the Pd-catalyzed heteroannulation of
N
-tosyl-
o
-bromoanilines and 1,3-dienes, engaging
diverse coupling partners for the preparation of 2-subsituted indolines,
including sterically demanding substrates that have not previously
been tolerated. Experimental and computational studies on model Pd-urea
and Pd-ureate complexes are consistent with monodentate binding through
the nonsubstituted nitrogen, which is uncommon for metal-ureate complexes.
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