BENZOTRIAZOLE-MEDIATED CONVERSIONS OF AROMATIC AND HETEROAROMATIC ALDEHYDES TO FUNCTIONALIZED KETONES

Aromatic and heteroaromatic aldehydes reacted with benzotriazole and triethyl orthoformate in THF to give the corresponding alpha-(benzotriazol-1-yl)aryl ethyl ethers 7 in good yield. The novel acyl anion precursors 7 underwent smooth lithiation at the methine group followed by trapping with alkyl halides, aldehydes, ketones, and imines to yield the expected substituted intermediates of type 9, which were hydrolyzed under mild conditions without isolation. Benzaldehyde, methyl-, chloro-, and methoxy-substituted benzaldehydes, 1-naphthalenecarboxaldehyde, 2- and 3-furaldehydes, 2- and 3-thiophenecarboxaldehydes, and 2-pyridinecarboxaldehyde were all transformed in this manner into a variety of aryl and heteroaryl ketones with alkyl (10), alpha-hydroxyalkyl (12 and 13), alpha-aminoalkyl (14) and acyl(15) substituents.