To avoid the formation of these products, the 4-position of
1c was substituted with a sulfonic acid sodium salt, and it
was electrolyzed. In this case the 1,3-dioxol (2d) was
successfully obtained in 87% yield.
Scheme 2
The physical and spectroscopical descriptions of the new
compounds 2a-e are provided in footnote 17.
Acknowledgment. This study was financed by the
Spanish MEC CTQ2004-05394/BQU. B.B. thanks the Span-
ish MCyT for the “Ramon y Cajal” financiation. The authors
want to express their gratefulness to the Prof. M. Folmer
Nielsen for all her kind suggestions.
OL050614E
(17) Phenanthrene[9,10-d]1,3-dioxole (2a) (817 mg, 92% yield). Mp
120-121 °C. IR (KBr) ν ) 3063, 2906, 1658, 1609, 1520, 1450, 1372,
1
1118, 1073, 751, 720 cm-1. H NMR (300 MHz, CDCl3) δ: 6.27(s, 2H),
7.57(t, 2H, J ) 7 Hz), 7.64(t, 2H, J ) 7 Hz), 7.94(d, 2H, J ) 7.8 Hz),
8.66(d, 2H, J ) 7.8 Hz). 13C NMR (75.4 MHz, CDCl3) δ: 101.77, 120.0,
121.2, 123.3, 124.7, 126.9, 127.3, 137.8. MS m/e (relative intensity) EI:
223(M+ + 1, 16), 222(M+, 100), 194(11), 180(11), 163(45), 152(6), 111-
(12), 82(15), 63(8). Anal. Calcd for C15H10O2: C, 81.08; H, 4.50. Found:
C, 81.27; H, 4.39. 1,10-Phenanthroline[5,6-d]1,3-dioxole (2b) (1098 mg,
98% yield). Mp 240-242°C. IR (KBr) ν ) 3058, 2921, 1661, 1590, 1517,
1
1459, 1364, 1067, 1027, 794, 734 cm-1. H NMR (300 MHz, CDCl3) δ:
6.32(s, 2H), 7.61(dd, 2H, J1 ) 8.1 Hz, J2 ) 4.4 Hz), 8.25(dd, 2H, J1 ) 8.1
Hz, J2 ) 1.8 Hz), 9.07(dd, 2H, J1 ) 4.4 Hz, J2 ) 1.8 Hz). 13C NMR (75.4
MHz, CDCl3) δ: 103, 118.2, 123.2, 128.3, 137.4, 142.8, 148.5. MS m/e
(relative intensity) EI: 225(M+ + 1, 15), 224(M+, 100), 196(6), 166(32),
139(20), 112(14), 88(5). Anal. Calcd for C13H8N2O2: C, 69.64; H, 3.57;
N, 12.50. Found: C, 69.39; H, 3.33; N, 12.71. Naphtho[1,2-d]1,3-dioxole
(2c) (320 mg, 37% yield). Mp 84-87°C. IR (KBr) ν ) 3058, 2887, 1650,
1604, 1466, 1413, 1281, 1060, 799 cm-1. 1H NMR (300 MHz, CDCl3) δ:
6.16(s, 2H), 7.2(d, 1H, J ) 8.6 Hz), 7.29-7.36(m, 1H), 7.4-7.48(m, 2H),
7.8(t, 2H, J ) 7.4 Hz). 13C NMR (75.4 MHz, CDCl3) δ: 101.8, 110.6,
119.8, 121.9, 124.1, 126.4, 128.6, 130.2, 141.3, 143.4. MS m/e (relative
intensity) EI: 173(M+ + 1, 12), 172(M+, 100), 171(M+ - 1, 72), 130(11),
114(55), 86(21), 74(11), 63(23), 51(12). Anal. Calcd for C11H8O2: C, 76.74;
H, 4.65. Found: C, 76.61; H, 4.82. 4-Sulfonic acid tetraethylammonium
salt-naphtho[1,2-d]1,3-dioxole (2d) (1657 mg, 87% yield). Mp 144-146°C.
IR (KBr) ν ) 3050, 2987, 1644, 1605, 1461, 1326, 1204, 1022, 763, 733,
630 cm-1. 1H NMR (300 MHz, CDCl3) δ: 0.82(t, 12H, J ) 7 Hz), 2.77(c,
8H, J ) 7 Hz), 6.0(s, 2H), 7.15-7.35(m, 2H), 7.62(d, 1H, J ) 8 Hz),
7.77(s, 1H), 8.72(d, 1H, J ) 7.7 Hz). 13C NMR (75.4 MHz, CDCl3) δ:
7.2, 52.0, 102.0, 110.8, 119.6, 119.8, 124.7, 126.1, 127.8, 137.2, 141.3,
142.3. MS m/e (relative intensity) ESI(-): 252(M+ + 1, 8), 251(M+, 100).
ESI(+): 131(M+ + 1, 11), 130(M+, 100). Anal. Calcd for C19H27NO5S:
C, 59.84; H, 7.09; N, 3.67. Found: C, 60.10; H, 6.92; N, 3.72. 5,6-
Dimethoxy-benzo[1,3]dioxole (2e) (164 mg, 18% yield). Mp 77-79°C.
IR (KBr) ν ) 3003, 2925, 1509, 1466, 1215, 1184, 1165, 1031, 925, 813
We can conclude that the more negative the E°′ values,
the higher are the yields of 2 obtained, and the reaction is
not a nucleophilic substitution but a homogeneous electron
transfer of the dianion to dichloromethane.
The electrogenerated dianion reacts with dichloromethane
in a redox process to afford the chloromethane radical
•CH2Cl, which then couples with the anion radical of quinone
to generate a C-O bond. Subsequently, an internal nucleo-
philic substitution leads to 2 in good yield (Scheme 2).
Furthermore, the experimental consumed charge was
always a little higher than expected (2 F/mol). This is in
agreement with our postulated mechanism in which the last
radical coupling is only effective when both species are in
near proximity. Therefore additional charge would ensure
complete consumption of the starting quinone.
The formation of dicarboxylic acids 3 is due to the
electron-transfer reaction of the remaining dianion to O2,
during the workup under open-air atmosphere.
In the reduction of 1,2-naphthoquinone (1c), together with
2c and dicarboxylic acid 3c, secondary products were formed.
cm-1 1H NMR (300 MHz, CDCl3) δ: 3.82(s, 6H), 5.88(s, 2H), 6.58(s,
.
2H). 13C NMR (75.4 MHz, CDCl3) δ: 57.3, 96.4, 101.2, 125.7, 140.9. MS
m/e (relative intensity) EI: 183(M+ + 1, 10), 182(M+, 100), 167(63), 121-
(18), 109(76), 81(49), 69(56), 53(77). Anal. Calcd for C9 H10 O4: C, 59.34;
H, 6.59. Found: C, 59.60; H, 6.68.
Org. Lett., Vol. 7, No. 13, 2005
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