Keywords: methyl ester of 4,4-dibromo-2,2-dimethyl-3-oxopentanoic acid, 9c-methyl-2-R-9b,9c-dihydro-5-oxa-2-azacyclopenta[2,3]cyclopropa[1,2-a]naphthalene-1,3,4-trione, zinc.We showed earlier that derivatives of 2-oxochromene-3-carboxylic acid are cyclopropanated by bromine-containing zinc enolates, obtained from 1-aryl-2,2-dibromoalkanones and zinc, to form cyclopropane derivatives containing an aroyl group on the ring as one of the functional substituents [1].In attempting to obtain cyclopropane derivatives containing a 3-methoxy-2,2-dimethyl-1,3-dioxopropyl moiety instead of an aroyl group, we studied the reaction of zinc enolate 1 (obtained from the methyl ester of 4,4-dibromo-2,2-dimethyl-3-oxopentanoic acid (2)) with N-substituted amides of 2-oxochromene-3-carboxylic acid 3a,b. However, we found that the reaction does not stop in the cyclopropanation step but rather we unexpectedly observe (see scheme) formation of the products of an additional intramolecular cyclization:Probably in ether-ethyl acetate-THF-HMPTA medium, the zinc enolate 1 regiospecifically reacts with the electrophilic substrates 3a,b to form the intermediates 4a,b. Stereospecific cyclization of intermediates 4a,b leads to synthesis of the corresponding cyclopropanation products 5a,b, in which the amide group and the keto ester moiety are located on the same side of the plane of the three-membered ring, making additional heterocyclization possible. We may hypothesize that the amide group attacks the ketone group to form intermediate 6a,b (which is stabilized in a process similar to acid cleavage reactions of acetoacetic ester) to form 9c-methyl-2-R-9b,9c-dihydro-5-oxa-2-azacyclopenta[2,3]cyclopropa[1,2-a]naphthalene-1,3,4-triones 7a,b.The structure of compounds 7a,b was proven by elemental analysis data and IR and 1 H NMR spectroscopy.The IR spectra include characteristic absorption bands for lactone carbonyls at 1745-1755 cm -1 and for lactam groups at 1695-1715 cm -1 and 1770-1800 cm -1 .In the 1 H NMR spectra, we observe characteristic signals in the 1.21-1.28 ppm (s) and 3.10-3.50 ppm (s) regions, respectively belonging to protons of the methyl group and the methine proton (CH).9c-Methyl-2-(4-methylphenyl)-9b,9c-dihydro-5-oxa-2-azacyclopenta[2,3]cyclopropa[1,2-a]-naphthalene-1,3,4-trione (7a). Yield 38%; mp 281-282°C. IR spectrum (vaseline oil)