REGIOSELECTIVE ACYLATIONS OF KETONES TO 1,3-DIKETONES VIA METALATED DIMETHYLHYDRAZONES

Acyclic and cyclic unsymmetrical ketones 1 are regioselectively acylated via their corresponding metalated dimethylhydrazones 3 by using acid chlorides or anhydrides, arylnitriles, ethyl formate, carbon disulfide/methyl iodide, alkyl chloroformates, dialkyl carbonates, phenyl isocyanate, or phenyl isothiocyanate as acylating agents. Subsequent acidic hydrolysis leads to the 1,3-diketones 6 in acceptable to excellent overall yields. The tautomeric structure of the product hydrazones 4, 5, 7, and 8 is determined. Cyanation of 3 with cyanogen bromide affords the alpha-cyano dimethylhydrazones 9.