Regioselectivity in the reactions of methoxydehydrobenzenes with furans. Part 3. 3-Methoxyfuran and methoxydehydrobenzenes and the chemistry of their adducts

Abstract

The cycloadditions of methoxydehydrobenzenes containing a 3-methoxy group and 3-methoxyfuran are highly regioselective. The adducts, 1,4-dihydro-2-methoxy-1,4-epoxynaphthalenes, undergo mild acid-catalysed hydrolysis providing, first, an isolable 1,2,3,4-tetrahydro-2-methoxy-1,4-epoxy-naphthalen-2-ol, and then a 3,4-dihydro-1,4-epoxynaphthalen-2(1H)-one. The chemistry of these ketones is explored. One of them, 3,4-dihydro-5-methoxy-1,4-epoxynaphthalen-2(1H)-one, readily undergoes catalytic reduction to yield the hexahydro-1,4-epoxynaphthalene-2,5(1H,4aH)dione. The X-ray molecular structure of this dione and of the 2-monobrosyl ester of the derived diol are reported. Treatment of the above adducts with trifluoroacetic acid and acetic anhydride provides a convenient synthesis of 1-acetoxy-2-methoxynaphthalenes.