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. Author manuscript; available in PMC: 2019 Nov 12.
Published in final edited form as: Angew Chem Int Ed Engl. 2018 Oct 18;57(46):15107–15111. doi: 10.1002/anie.201808305

Figure 3.

Figure 3.

Synthetic access to dihydrobenzofurans. A: Formation of hemiketal-stabilized hydroquinone-quinone hybrid 3. i) 6.0 equiv. (NH4)2Ce(NO3)6, CH3CN/H2O, 0 °C to r.t., 30 min, 67% (2), 44% (2a), 68% (2b). ii) NMR study: 1.0 equiv. 2 (20 mg scale), 2.0 equiv. 2-methoxyhydroquinone, DMSO-d6, r.t., overnight, quantitative conversion to 3. Preparative scale: 2.0 equiv. 2-methoxyhydroquinone, acetone, r.t., overnight, contains trace amounts of 4, 94% (3), 78% (3a), 42% (in toluene, 3b). B: Preparation of dihydrobenzofuran 4. iii) 3.0 equiv. Hünig’s base, toluene, r.t., overnight, 73% (I-4 and u-4), 81% (I-4a and u-4a), 44% (I-4b and u-4b). C,D: Thermal ellipsoid plots (50% probability level) of X-ray structures. u-4: One co-crystallized acetone is omitted for clarity.