Bromine-containing organozinc compounds generated from 1,1-dibromo-3,3-dimethylbutan-2-one reacted with 2-arylmethylideneindan-1,3-diones and 5-arylmethylidene-2,2-dimethyl-1,3-dioxane-4,6-diones to give 3-aryl-2-(2,2-dimethylpropanoyl)spiro[cyclopropane-1,2′-indan]-1′,3′-diones and 1-aryl-6,6-dimethyl-2-(2,2-dimethylpropanoyl)-5,7-dioxaspiro[2.5]octan-4,8-diones, respectively. Reactions of 2-arylmethylideneindan-1,3-diones with bromine-containing zinc enolates derived from 1-aryl-2,2-dibromopropan-1-ones and 2,2-dibromo-1,2,3,4-tetrahydronaphthalen-1-one resulted in the formation of 2-aroyl-3-aryl-2-methylspiro-[cyclopropane-1,2′-indan]-1′,3′-diones and 2,3 : 8,9-dibenzo-12-phenyldispiro[4.0.5.1]dodecane-1,4,7-trione, respectively.We previously developed a procedure for the synthesis of spirocyclopropanes via reaction of 3-aryl-2-cyanoprop-2-enoic acid derivatives with zinc enolates derived from 2,2-dibromo-1,2,3,4-tetrahydronaphthalen-1-one and 2,2-dibromoindan-1-one [1]. In the present work we made an attempt to find out another synthetic approach to cyclopropane derivatives having one and two spiro carbon atoms. For this purpose, we examined reactions of bromine-containing organozinc compounds derived from α,α-dibromo ketones with 2-arylmethylideneindan-1,3-diones and 5-arylmethylidene-2,2-dimethyl-1,3-dioxane-4,6-diones. In fact, these reactions led to the formation of the corresponding cyclopropanation products as shown in Scheme 1.Zinc enolate II preliminarily generated from 1,1-dibromo-3,3-dimethylbutan-2-one I added at the double C=C bond in substrates IIIa, IIIb, IVa, and IVb to give intermediates Va, Vb, VIIa, and VIIb which underwent cyclization with formation of cyclopropanation products, 1-aryl-6,6-dimethyl-2-(2,2-dimethylpropanoyl)-5,7-dioxaspiro[2.5]octane-4,8-diones VIa and VIb and 3-aryl-2-(2,2-dimethylpropanoyl)spiro[cyclopropane-1,2 ′ -indan]-1′,3′-diones VIIIa and VIIIb (Scheme 1).
