Lewis Acid‐Catalyzed Ring‐Opening Functionalizations of 1,4‐Epoxy‐1,4‐dihydronaphthalenes

Abstract

Since 1,4-epoxy-1,4-dihydronaphthalenes are smoothly converted to 1-naphthol derivatives via unstable cation intermediates formed by the acid-catalyzed ring-opening reaction of the 1,4-epoxy moiety of 1,4-epoxy-1,4-dihydronaphthalenes, their nucleophilic functionalization using the cation intermediates as an active species is extremely difficult. We have accomplished the Lewis acid-catalyzed carboncarbon and carbon-nitrogen bond formations associated with the ring-opening of 1,4-epoxy-1,4-dihydronaphthalenes using nucleophiles such as allyltrimethylsilanes, trimethylsilyl cyanide and trimetylsilyl azide, by using the stabilization effect of the cation intermediate based on the introduction of appropriate substituents into the bridgehead positions of 1,4epoxy-1,4-dihydronaphthalenes to give the corresponding unique and multifunctionalized naphthalene derivatives. The present reactions could provide excellent regioselective functionalization methods using unsymmetrical substrates, which are quite difficult to achieve using transition metal-induced procedures. 521 Lewis Acid-Catalyzed Ring-Opening Functionalizations of 1,4-Epoxy-1,4-dihydronaphthalenes Scheme 5. Ring-opening functionalizations using nitrogenbridged substrate (11).Scheme 4. Proposed reaction mechanism.

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