The First Crystallographic Evidence for the Structures ofortho-Lithiated Aromatic Tertiary Amides

Despite the near-perpendicular arrangement of the amide group and aromatic ring in many tertiary aromatic amides, ortho-lithiation is still a very straightforward process. The first X-ray crystal structures of ortho-lithiated amides reveal why: the angle of twist is lessened to some degree, and the lithium ion lies far from the plane of the aromatic ring, with stabilization of the strained structure being achieved by dimerization (see scheme).