Pyridine-3-carbaldehyde Vilsmeier-Haack reaction

Several enamides, for example compound (72 Scheme 5), have been used as precursors to 1 -sub-stituted-2-pyridone derivatives (73) and pyridine-3-carbaldehyde derivatives (74 14-69%). Salt (1) promotes dehydration of tautomers (75b) of 2-acetylbenzamide derivatives (75a) to give enamides (76), which are converted by further reaction with salt U) into iminium salts (77). Hydrolysis of these salts yields aldehydes (78 81-99% Scheme 5). Enecarbamates, such as (79), give formylation products (80 26-94%) in the Vilsmeier-Haack reaction (Scheme 5). ... 

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