J=7.4 Hz, 2H), 2.47 (s, 3H), 1.35 (d, J=6 Hz, 6H), 1.10 (t, J=7.6 Hz, 3H); 13C NMR (CDCl3, 200 MHz) • 185.4, 182.0, 156.5, 144.9, 138.2, 133.9, 132.3, 129.5, 126.7, 126.5, 75.9, 23.3, 22.0, 17.5, 13.4. HRMS: m/z calcd. for C16H19O3 [MH+]: 259.1334. Found: 259.1333.
2-Hydroxy-3-ethyl-6-methyl-1,4-naphthoquinone (29). Gold needles (91%); (Rf = 0.57) (20% EtOAc/hexanes), mp 140-142 ºC. Anal. Calc. for C13H12O3; C, 72.21 ; H, 5.59. Found: C, 72.09; H, 5.87. IR (KBr, cm-1) 3353 (m), 2967 (m), 1639 (m), 1595 (m), 1258 (m); 1H NMR (CDCl3, 200 MHz) • 7.96 (d, J=8 Hz, 1H), 7.92 (bs, 1H), 7.46 (d, J=8.1 Hz, 1H), 7.35 (bs, 1H), 2.59 (q, J=7.4 Hz, 2H), 2.47(s, 3H), 1.12 (t; J=7.5 Hz, 3H); 13 C NMR (CDCl3, 200 MHz) • 185.1, 181.5, 153.0, 146.5, 133.6, 133.1, 127.5, 127.3, 126.5, 125.7, 22.3, 16.9, 12.9. HRMS: m/z calcd. for C13H13O3 [MH+]: 217.0865. Found: 217.0865.
2-Ethyl-3-isopropoxy-4-hydroxy-4-p-methoxyphenyl-2-cyclobutene-1-one(12). White crystals (44%) (Rf = 0.12) (20% EtOAc/hexanes), mp 83-85 ºC. Anal. Calcd. for C16H20O4; C, 69.54 ; H, 7.30. Found: C, 69.23 ; H, 7.55. IR (KBr, cm-1) 3322 (m), 2978 (m), 1744 (m), 1654 (s), 1255 (s), 1098 (s); 1H NMR (CDCl3, 200 MHz) • 7.40 (d, J=8.4 Hz, 2H), 6.89 (d, J=8.8 Hz, 2H), 4.71 (hept, J=6.3 Hz, 1H), 3.9 (bs, 1H), 3.81 (s, 3H), 2.19 (q, J=7.6 Hz, 2H), 1.38 (d, J=6.2 Hz, 3H), 1.18 (t, J=7.7 Hz, 3H), 1.15 (d, J=6 Hz, 3H); 13C NMR (CDCl3, 200 MHz) • 191.1, 181.2, 159.6, 130.0, 129.5, 122.1, 114.1, 92.4, 55.5, 22.9, 22.6, 15.9, 12.1. HRMS: m/z calcd. for C16H21O4 [MH+]: 277.1440. Found: 277.1439.
2-Isopropoxy-3-ethyl-6-methoxy-1,4-naphthoquinone (21). Yellow solid (70%); (Rf =0.56) (20% EtOAc/hexanes), mp 55-57 ºC. Anal. Calcd. for C16H18O4; C, 70.06 ; H, 6.61. Found : C, 69.85 ; H, 6.92. IR (KBr, cm-1) 2980 (m), 1735, 1718 (s); 1689, 1647, 1595 (s), 1260, 1239, 210 (s), 1107 (s); 1H NMR (CDCl3, 200 MHz) • 7.94 (dd, J=1.0, 8.7 Hz, 1H), 7.48 (dd, J=1.2, 3.0 Hz, 1H), 7.10 (dd, J=2.8, 8.7 Hz, 1H), 5.09 (hept, J=6.2 Hz, 1H), 3.92 (s, 3H), 2.59 (q, J=7.6 Hz, 2H), 1.34 (d, J=6.2 Hz, 6H), 1.09 (t, J=7.5 Hz, 3H); 13C NMR (CDCl3, 200 MHz) • 185.5, 181.1, 164.2, 156.7, 137.8, 134.5, 128.7, 125.2, 119.6, 109.8, 76.0, 56.0, 23.2, 17.5, 13.3. HRMS: m/z calcd. for C16H19O4 [MH+]: 275.1283. Found: 275.1280.
2-Hydroxy-3-ethyl-6-methoxy-1,4-naphthoquinone (30). Yellow solid (79%); (Rf = 0.45) (20% EtOAc/hexanes), mp 128-130 ºC. Anal. Calcd. for C13H12O4; C, 67.23 ; H, 5.21. Found : C, 67.15 ; H, 5.55. IR (KBr, cm-1) 3342 (s), 2965 (m), 1642 (s), 1587 (s), 1242 (s); 1H NMR (CDCl3, 200 MHz) • 8.01 (d, J=8.4 Hz, 1H), 7.58 (d, J=3 Hz, 1H), 7.44 (bs, 1H), 7.11 (dd, J=2.3, 8.2 Hz, 1H), 3.95 (s, 3H), 2.60 (q, J=7.4 Hz, 2H), 1.14 (t, J=7.5 Hz, 3H); 13C NMR (CDCl3 200MHz) 184.7, 180.5, 165.4, 153.2, 135.7, 128.9, 125.2, 122.8, 119.2, 111.0, 56.2, 16.9, 12.9. HRMS: m/z calcd. for C13H13O4 [MH+]: 233.0814. Found: 233.0813.
Electrochemical studies
All the experiments corresponding to cyclic voltammetry were recorded in a Electrochemical Analyser BAS-100 with a typical three electrodes arrangement. Ag /AgCl, 7 mm2 glassy carbon and platinum as reference, working and auxiliary electrodes respectively. Dry acetonitrile was used as solvent which was dried over anhydrous CaCl2, and distilled from CaH2. Dry tetrabutylammonium hexafluorophosphate was used as support electrolyte, which was dried by
