The comprehensive study of the reactions of carbonylcompounds and ethyl diazoacetate in the presence of a Brønsted acid catalyst is described. In result, a broad range of 3-oxo-esters were synthesized from a variety of ketones and aliphatic aldehydes by 1,2-aryl/alkyl/hydride shift. Aryl–methyl ketones produced only aryl-migrated products, whereas other ketones yielded a mixture of products. For diaryl