348.3 (95), 320.3 (76), 292.3 (51), 264.3 (29), 213.2 (22), 198.2 (22), 169.2
(27), 155.2 (42), 115.1 (58), 91.1 (76), 66.1 (27).
for Diels–Alder reactions in water are larger than those in organic
solvents.2
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Notes and references
{ Synthesis of 3 and 3a: A solution (ca. 100 mL) of lithium perchlorate
solution (0.3 M) in ethanol–water (80 : 20 v/v) containing 5 mmol of
catechol (1), 20 mmol of cyclopentadiene (2) and 1 ml acetic acid was
electrolyzed in an undivided cell equipped with a glassy carbon anode (an
assembly of two rods) and a large platinum gauze as cathode, at 25 uC at
0.8 V vs. SCE, in a dark cell. The electrolysis was terminated when the
current decayed to 5% of its original value. The resulting yellow solution
was concentrated under reduced pressure and the residue was extracted
with benzene. The extracted portion was washed with water, dried over
MgSO4 and concentrated. The residue (0.8 g) was maintained below 25 uC
for several days in diethyl ether. The resulting yellow–orange crystals (3)
(mp 87–89 uC (lit. 89–91 uC4a,b,7)) and orange crystals (3a) (mp 137–139 uC
(lit. 139–141 uC4a,b)) were obtained and characterized by comparison of
their spectra and physical data with those obtained by the literature
method.4,7
§ Synthesis of 4: Electrolysis was performed in a normal glass cell. The
general procedure was the same as was described for 3 and 3a. The
resulting yellow solution was concentrated under reduced pressure
and the residue was extracted with benzene. The extracted portion was
washed with water, dried over MgSO4 and concentrated. The residue was
washed with acetone several times. The resulting yellow powder (0.56 g)
(mp 223–225 uC) was characterized by IR (KBr) (cm21): 2901, 2855, 1733,
1709, 1446, 1352, 1311, 1297, 1256, 1176, 1094; 1H NMR: d ppm
(400 MHz, CDCl3): 2.10 (m, 1H), 2.15 (m, 1H), 2.28 (m, 2H), 2.40 (m, 2H),
2.89 (m, 2H), 3.20 (m, 4H), 3.46 (m, 2H), 3.64 (m, 2H), 5.40 (m, 2H),
5.56 (m, 2H); 13C NMR, d ppm (400 MHz, CDCl3): 31.9, 37.6, 43.0, 47.4,
52.9, 54.1, 60.6, 129.1, 133.5, 196.6, 197.4; MS (m/z) (relative intensity):
3 A. J. Bard and L. R. Faulkner, Electrochemical Methods, 2nd edn, Wiley,
New York, 2001, p. 497.
4 (a) M. F. Ansell, A. F. Gosden and V. J. Leslie, Tetrahedron Lett., 1967,
8, 4537–4540; (b) M. F. Ansell and A. F. Gosden, Chem. Commun.
(London), 1965, 520–521; (c) M. F. Ansell, A. F. Gosden, V. J. Leslie and
R. A. Murray, J. Chem. Soc. C, 1971, 1401–1414; (d) W. M. Horspool,
J. M. Tedder and Z. U. Din, Chem. Commun. (London), 1966, 775–776.
5 R. Greef, R. Peat, L. M. Peter, D. Pletcher and J. Robinson, Instrumental
Methods in Electrochemistry, Ellis Horwood, Chichester, UK, 1990,
p. 189.
6 (a) E. S. Gawalt and M. Mrksich, J. Am. Chem. Soc., 2004, 126,
15613–15617; (b) Y. Kwon and M. Mrksich, J. Am. Chem. Soc., 2002,
124, 806–812; (c) M. N. Yousaf, E. W. L. Chan and M. Mrksich, Angew.
Chem., Int. Ed., 2000, 39, 1943–1946; (d) M. N. Yousaf and M. Mrksich,
J. Am. Chem. Soc., 1999, 121, 4286–4287.
7 (a) P. Burn, P. A. Cooks, F. H. Ley, B. Costall, R. J. Naylor and
V. Nohria, J. Med. Chem., 1982, 25, 363–368; (b) F. J. Evans,
H. S. Wilgus, III and J. W. Gates, Jr, J. Org. Chem., 1965, 30, 1655–1657.
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