Diazoaldehyde Chemistry: Part 4 - Vilsmeier-Haack Formylation of Diazo Compounds: A Re-investigation

Article abstract of DOI:10.1002/hlca.19970800327

Diazomethyl ketones (2-diazoethanones) were reacted with the Vilsmeier reagent ((chloromethylidene)dimethylammonium chloride) to yield α-diazo-β-oxoaldehydes and chloromethyl ketones. 2′,4′-Dimethoxy-α-diazoacetophenone gave 2-chloro-1-(2,4-dimethoxyphenyl)-3-(dimethylamino)prop-2-en-1-one (5) in addition to the expected products. Phenyldiazomethanes gave the corresponding benzyl chlorides but not the (phenyl)diazoacetaldehydes even at temperatures as low as -60°. The diazo-transfer reactions of phenylacetaldehydes and 2-azido-1-ethylpyridin-1-ium tetrafluoroborate also did not yield the expected(phenyl)diazoacetaldehydes.