Étude de la metallation des carbamates d'hydroxy-2,3,4 quinoléines

When N,N-dialkyl O-(quinolyl-3 or 4) carbamates are reacted with LDA in THF at −78 °C lithiation occurs regioselectively at the ortho positions (respectively at C4 and C3). With the 2-substituted isomer better results can be obtained by using sec-butyllithium/TMEDA chelate instead of LDA in THF at −105 °C. Each of the lithiated intermediates is treated with various electrophiles. The results of experiments with aldehydes afford convincing evidence of the influence of steric hindrance around the nitrogen of the carbamate functional group. Various disubstituted hydroxyquinolines have been prepared.