New synthetic approach to naphtho[1,2-b]furan and 4 '-oxo-substituted spiro[cyclopropane-1,1 '(4 ' H)-naphthalene] derivatives

A one-step synthesis of ethyl 2,3-dihydronaphtho[1,2-b]furan-2-carboxylate and/or ethyl 4'-oxospiro[cyclopropane-1,1'(4'H)-naphthalene]-2'-carboxylate derivatives 2 and 3, respectively, from substituted naphthalen-1-ols and e thyl 2,3-dibromopropanoate is described (Scheme 1). Compounds 2 were easily aromatized (Scheme 2). In the same way, 3,4-dibromobutan-2- one afforded t he corresponding 1-(2,3-dihydronaphtho[1,2-b]-furan-2-yl)ethanone and/or sp iro derivatives 8 and 9, respectively (Scheme 6). A mechanism for the forma tion of the dihydronaphtho[1,2-b]furan ring and of the spiro compounds 3 is proposed (Schemes 3 and 4). The structures of spiro compounds 3a and 3f we re established by X-ray structural analysis. The reactivity of compound 3a was also briefly examined (Scheme 9).