Reactions of zinc enolates formed from 2,2-dibromoindan-1-one or 2,2-dibromo-3,4-dihydronaphthalen-1(2H)-one and zinc with alkyl 5,5-dimethyl-2-oxo-2,5-dihydrofuran-3-carboxylates

Abstract

Reactions of derivatives of 3-aryl-2-cyanopropenoic acid with zinc enolates obtained from dibromotetralone or dibromoindanone and zinc are known to result in substituted spirocyclopropanes [1].Boiling of alkyl 5,5-dimethyl-2-oxo-2,5-dihydrofuran-3-carboxylates Ia, Ib in a mixture ether-ethyl acetate for 40 min with zinc enolates II, III obtained by the reaction of 2,2-dibromoindan-1-one or 2,2-dibromo-3,4-dihydronaphthalen-1(2H)-one with zink afforded in good yields O Br Br OZnBr Br O Br Br OZnBr Br Zn Zn O O COOAlk H Me Me O H ZnBr Br O O Me Me COOAlk O O Me Me O H COOAlk _ ZnBr 2 n n Iа, Ib VIа, VIb, VII IVа, IVb, V II III II, III alkyl 4,4-dimethyl-2,1'-dioxo-3-oxaspiro[bicyclo[3.1.0] heptan-6,2'-indan]-1-carboxylates IVa, IVb and 4,4-dimethyl-2,1'-dioxo-3-oxaspiro(bicyclo[3.1.0]heptan-6,2'-tetralin)-1-carboxylate (V), whose structure was established by 1 H and 13 C NMR spectroscopy. The assignment of signals in the 1 H, 13 C NMR spectra was performed based on analysis of the data of 2D experiments HSQC, HMBC, NOESY. Synthesis of compounds IVa, IVb and V apparently I, Alk = Me (a), Et (b); IV, VI, n = 1, Alk = Me (a), Et (b); V, VII, n = 2, Alk = Et.