Abstract
Unexpectedly, lithiation of N'-(2-(2-methylphenyl)ethyl)-N,N-dimethylurea with 3 equiv of n-butyllithium in anhydrous THF at 0 degrees C takes place on the nitrogen and on the CH2 next to the 2-methylphenyl ring (alpha-lithiation). The lithium reagent thus obtained reacts with various electrophiles to give the corresponding substituted derivatives in excellent yields. Similarly, lithiation of N-(2-(2-methylphenyl)ethyl)pivalamide under similar reaction conditions followed by reaction with benzophenone as a representative electrophile gave the corresponding alpha-substituted product in high yield. Surprisingly, no products resulting from lateral lithiation were observed under the conditions tried, which sharply contrasts with the reported results for lateral lithiation of tert-butyl (2-(2-methylphenyl)ethyl)carbamate.