Regioselective Alkylations of Cyclic 1,3-Diketones via Metalated Dimethylhydrazones

Cyclic 1,3- diketones 1 are transformed into their 2,2-dimethylhydrazones 2 , which can be alkylated regio-selectively at different positions after mono-, di-, tri-, and tetrametalation. Monometalated C-2 unsubstituted hydrazones afford C-2 and N-alkylation, monometalated C-2 substituted hydrazones afford only C-2 alkylation. The regioselectivity of the alkylation of the polymetalated hydrazones follows Hauser's rule according to the sequence: NH- > C-4 Ha > C-5 > C-4 Hb. Hydrolysis of the product hydrazones 3–5 afforded mono- and polyalkylated 1,3- diketones 7 in good yields.