Molecular Structures of a Lithiated Schiff Base and a Related Dialkyl Ketone Imine

The ether‐solvated lithium derivative of pinacolone anil (2a) is shown to be a centrosymmetric dimer (1) by X‐ray diffraction analysis. Each lithium atom is bound to two nitrogen atoms, to the oxygen atom of diethyl ether, and weakly to two carbon atoms of a phenyl ring, but not to the vinyl moiety of the enamide anion. Despite conformational deconjugation, 1 is methylated at the carbon atom by methyl iodide. 1H‐NMR shifts of 1 in solution are solvent‐dependent. The results are discussed with respect to the “syn effect” in 1‐azaallyl anions. The molecular structure of the dianil 3 of 2,2,7,7‐tetramethyl‐3,6‐octanedione shows that a CH proton may approach the π face of an aromatic carbon atom down to a nonbonding distance of 274 A without causing much strain.