The cycloadditions of met hoxydehydrobenzenes containing a 3met hoxy group and 3met hoxyfuran 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-epoxynaphthalen-2-01, and then a 3,4-dihydro-l,4-epoxynaphthalen-2(1 H ) -o n e . The chemistry of these ketones is explored. One of them, 3,4-dihydro-5-methoxy-l,4-epoxynaphthalen-2( 1 H ) -one, readily undergoes catalytic reduction t o yield the hexahydro-l,4-epoxynaphthalene-2,5( 1 H,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.14 could be isolated by fractional crystallization of the crude epoxynaphthalen-2(1H)-one 23 (Scheme 4) (1-H, 6, 5.29 and product. The structural assignment of the hemiacetal 14 is 4-H, 8, 5.88). Therefore the 5-methoxy ketone 15 is that based on its spectral data. The IR spectrum exhibited a band at ketone in which 1-H resonates at 6, 5.01 and 4-H at 6, 5.89. 3370 cm-' attributed to an OH stretching frequency. The ''C and the 8-methoxy ketone 16 is the one in which 1-H resonates NMR spectrum revealed a signal for the methoxy group of the at 6, 5.24 and 4-H at 6, 5.69. in their respective ' H NMR hemiacetal at 6, 50.06, a quaternary carbon atom attributed to spectra. Similar assignments allow distinctions to be made C-2 resonating at 6, 106.39, and the methylene carbon signal between the pairs of ketones 31/32 (Scheme 5), 38/39 (Scheme 6) at 6, 43.02 was attributed to C-3. Nuclear Overhauser effect and 52153 (Scheme 8). (NOE) difference spectroscopy gave evidence for the stereochemistry and the results are shown in Fig. I . Significant interactions are those between the endo-methoxy group at C-2 and both the bridgehead proton 1-H and 3-H,,d,, and between 3-H,,, and the eso-hydroxy group at C-2. Nucleophilic attack by water therefore occurs exclusively from the e.uo-face of the adduct and this mode of attack presumably reflects the unhindered nature of this face of the molecule compared with the endo-face. The spectroscopic properties of the hemiacetal 4 derived from the parent adduct 2 are similar to those of the methoxy derivative 14. In this case the infrared O H stretching 23 9% 19 5% n 39 7% 9 3%* See under section 5.6.

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