DIAZOALDEHYDE CHEMISTRY .4. VILSMEIER-HAACK-FORMYLATION OF DIAZO-COMPOUNDS - A REINVESTIGATION

Diazomethyl ketones (2-diazoethanones) were reacted with the Vilsmeier reagent ((chloromethylide)dimethylammonium chloride)to yield alpha-di azo-beta-oxoaldehydes and chloromethyl ketones. 2',4'-Dimethoxy-alpha- diazoacetophenone gave -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)diazoacetaldeh ydes even al temperatures as low as - 60 degrees. The diazo-transfer r eactions of phenylacetaldehydes and 2-azido-1-ethylpyridin-1-ium tetra fluoroborate also did not yield the expected(pheny)diazoacetaldehydes.