In the presence of a gold catalyst, the ring opening of 1,4-epoxy-1,4-dihydronaphthalenes with allyltrimethylsilane affords allylnaphthalenes in high yield. For unsymmetrical substrates, high regioselectivity is observed in many cases. This reaction might proceed via tricyclic tetrahydrofuran intermediates which are formed stereoselectively.

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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Lewis Acid-Catalyzed Ring-Opening Functionalizations of 1,4-Epoxy-1,4-dihydronaphthalenes. -A novel Lewis acid-catalyzed ring-opening allylation, cyanation and azidation of 1,4-disubstituted 1,4-epoxynaphthalenes is reported. Highly functionalized naphthalene derivatives (III)/(IV), (VI),(IX), (X), and (XIII) are obtained via regioselective C-C and C-N bond formation. -(SAWAMA*, Y.; OGATA, Y.; KAWAMOTO, K.; SATAKE, H.; SHIBATA, K.; MONGUCHI, Y.; SAJIKI, H.; KITA, Y.; Adv. Synth. Catal. 355 (2013) 2-3, 517-528, http://dx.doi.org/10.1002/adsc.201200771 ; Gifu Pharm. Univ., Gifu 501-11, Japan; Eng.) -S. Karsten 30-102