J. C. de Mendonc¸a Ca6alcanti et al. / Tetrahedron Letters 43 (2002) 6343–6345
2.63), 4.25 (q, 2H, J=7 Hz), 4.1 (m, ABX
6345
In summary, we have explored two routes to prepare
6
, 1H), 3.2–3.1
medium-sized lactones based on the electrochemical
arylation of activated olefins catalysed by a nickel
complex. The route based on the intramolecular C,C-
bond formation does not seem to be general enough, at
least in the selected reaction conditions. We have how-
ever found an interesting alternative which is based on
the bimolecular coupling between an ortho-substituted
aryl halide and an a,b-unsaturated ester, followed by
the lactonisation.
(m, ABX, 2H, J=16.91, 6.59, 6.37, Dw/J=2.38), 1.3 (t,
3H, J=7 Hz); 13C NMR (50.32 MHz, CDCl3): l 171.8,
171.3, 133.1, 132.0, 128.8, 127.3, 124.9, 124.0, 69.3, 61.0,
41.1, 32.4, 14.0; MS (EI) m/z (rel. intensity): 234 (5), 188
(100), 160 (56), 146 (13), 115 (31), 103 (6), 91 (8); IR
(KBr) w (cm−1): 3015, 2931, 1735, 1601, 1580.
5. 9 (40%): 1H NMR (200 MHz, CDCl3): l 7.2–6.7 (m, 4H),
3.3 (q, 1H, J=7.6 Hz), 3.1 (s, 3H), 1.37 (d, 3H, J=7.6
Hz); 13C NMR (50.32 MHz, CDCl3): l 178.6, 143.8,
130.5, 128.7, 123.3, 122.3, 107.8, 40.4, 26.0, 15.3; MS (EI)
m/z (rel. intensity): 161 (100), 146 (46), 132 (26), 118 (70),
91 (24), 77 (5), 65 (4), 51 (5); IR (KBr) w (cm−1): 3014,
2936, 2253, 1702, 1615, 1494, 1351.
Acknowledgements
The authors thank the CAPES/COFECUB exchange
program for financial support.
6. Fox, M. A.; Chandler, D. A.; Lee, C. J. Org. Chem. 1991,
56, 3246–3255.
7. Greene, T. W.; Wuts, P. G. M. Protective Groups in
Organic Synthesis; John Wiley: New York, 1991; pp.
10–142.
References
8. For formation and cleavage of tetrahydropyranyl ethers,
see: Bernady, K. F.; Brawner Floyd, M.; Poletto, J. F.;
Weiss, M. J. J. Org. Chem. 1979, 44, 1438–1447.
9. Boyd, G. V. The chemistry of lactones and lactams, In
The Chemistry of Acid Derivatives; Patai, S., Ed; John
Wiley: New York, 1979, Part 1, supplement B, pp. 491–
531.
10. (a) Grieco, P. A.; Nishizawa, M.; Oguri, T.; Burke, S. D.;
Marinovic, N. J. Am. Chem. Soc. 1977, 99, 5773–5780;
(b) Grieco, P. A.; Noguez, J. A.; Masaki, Y. J. Org.
Chem. 1977, 42, 495–502.
1. Ne´de´lec, J. Y.; Pe´richon, J.; Troupel, M. Topics Curr.
Chem. 1997, 185, 141–173.
2. (a) Condon-Gueugnot, S.; Le´onel, E.; Ne´de´lec, J. Y.;
Pe´richon, J. J. Org. Chem. 1995, 60, 7684–7686; (b)
Condon, S.; Dupre´, D.; Falgayrac, G.; Ne´de´lec, J. Y.
Eur. J. Org. Chem. 2002, 1, 105–111; (c) Gomes, P.;
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3. Typical electrochemical procedure: The undivided cell was
equipped with a nickel foam (15 cm2) as the cathode and
an iron rod as the anode. A short electrolysis was first
conducted at constant current intensity (0.15 A) and at
room temperature for 30 min with the (9/1) DMF/pyri-
dine solution containing tetrabutylammonium bromide
(200 mg) as supporting electrolyte and 1,2-dibromoethane
in order to generate a small amount of iron ions. After
the addition of NiBr2·3H2O (20% vs aryl halide) and the
reagent (route A) or the mixture of reagents (route B),
the electrolysis was run at constant current intensity (0.05
A for route A, 0.15 A for route B) at 100°C. After usual
work-up, the product was isolated by column chromato-
graphy on silica gel (230–400 mesh) using pentane/ether
as eluent. The products were fully characterised by 1H
NMR, 13C NMR, MS and IR analysis.
11. 6b (62%): 1H NMR (200 MHz, CDCl3): l 7.3–7.0 (m,
4H), 3.4 (s, 2H), 2.9 (dd, 2H, J=8.1, 7.5 Hz), 2.5 (dd,
2H, J=8.1, 7.5 Hz); 13C NMR (50.32 MHz, CDCl3): l
173.6, 140.2, 139.6, 129.5, 128.9, 128.0, 126.8, 62.6, 35.5,
27.7; MS (EI) m/z (rel. intensity): 162 (30), 144 (26), 133
(20), 134 (6), 118 (21), 117 (100), 105 (18), 91 (46); IR
(KBr) w (cm−1): 3030, 2980, 1731, 1600, 1580.
12. 6c (60%) mp 61–62°C: 1H NMR (200 MHz, CDCl3): l
7.0 (s large, 4H), 3.7 (t, 2H, J=7.2 Hz), 2.8–3.0 (m, 4H),
2.5 (m, 2H); 13C NMR (50.32 MHz, CDCl3): l 180.7,
143.8, 141.5, 134.9, 133.9, 131.5, 131.4, 68.0, 40.6, 40.1,
32.5; MS (EI) m/z (rel. intensity): 176 (32), 161(7), 146
(88), 131 (51), 117 (30), 104 (100), 91 (73), 78 (31); IR
(KBr) w (cm−1): 3014, 2980, 1712, 1492.
4. 5b (20%): 1H NMR (200 MHz, CDCl3): l 7.3–7.0 (m,
4H), 5.45–5.3 (2d, AB system, 2H, J=13.8 Hz, Dw/J=