Journal
SYNTHESIS-STUTTGART
Volume 44, Issue 13, Pages 2013-2022Publisher
GEORG THIEME VERLAG KG
DOI: 10.1055/s-0031-1291008
Keywords
N '-phenethyl-N,N-dimethylurea; side-chain lithiation; bromine-lithium exchange; electrophile; synthesis
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Funding
- Cardiff University
- Saudi Government
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Lithiation of N'-phenethyl-N,N-dimethylurea with three equivalents of tert-butyllithium in anhydrous tetrahydrofuran at -78 degrees C takes place on the nitrogen and on the side-chain of the CH2 next to the phenyl ring (alpha-lithiation). The 2-lithio isomer can be obtained via bromine-lithium exchange of N'-2-(2-bromophenyl)ethyl-N,N-dimethylurea using methyllithium followed by tertbutyllithium in tetrahydrofuran at -78 degrees C. The lithium reagents thus obtained react with various electrophiles to give the corresponding substituted derivatives in excellent yields. Lithiation of N'-(3-phenylpropyl)-N, N-dimethylurea takes place on the alpha-CH2 with tert-butyllithium at 0 degrees C. On the other hand, lithiation of N'-(4phenylbutyl)-N,N-dimethylurea with tert-butyllithium at 0 degrees C takes place on one of the methyl groups of the urea unit.
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