Diazoaldehyde Chemistry. Part 4<i>vilsmeier‐haack</i> formylation of diazo compounds: A re‐investigation

Abstract

Abstract 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.