H-5), 2.88 (br s, 2H, H-1 and H-4), 1.71 (ddd, J3n,3x = 11.1, J2,3x
=
Harrity, J. Am. Chem. Soc., 2007, 129, 2691–2699; (f) M. D. Helm, A.
Plant and J. P. A. Harrity, Synlett, 2007, 2885–2887; (g) D. L. Browne,
M. D. Helm, A. Plant and J. P. A. Harrity, Angew. Chem., Int. Ed.,
2007, 46, 8656–8658; (h) P. M. Delaney, D. L. Browne, H. Adams, A.
Plant and J. P. A. Harrity, Tetrahedron, 2008, 64, 866–873; (i) P. M.
Delaney, J. Huang, S. J. F. Macdonald and J. P. A. Harrity, Org. Lett.,
2008, 10, 781–783; (j) D. L. Browne, J. F. Vivat, A. Plant, E. Gomez-
Bengoa and J. P. A. Harrity, J. Am. Chem. Soc., 2009, 131, 7762–7769;
(k) R. S. Foster, J. Huang, J. F. Vivat, D. L. Browne and J. P. A. Harrity,
Org. Biomol. Chem., 2009, 7, 4052–4056; (l) D. L. Browne and J. P. A.
Harrity, Tetrahedron, 2010, 66, 553–568.
4 (a) D. S. Matteson and J. Wasserbillig, J. Org. Chem., 1963, 28, 366–
369; (b) K. Kiyoshi, G. W. Willcockson, I. S. Bengelsdorf, and W. G.
Woods, US Pat. 3135781, 1964; (c) W. G. Woods and I. S. Bengelsdorf,
J. Org. Chem., 1966, 31, 2769–2772; (d) D. S. Matteson and M. L.
Talbot, J. Am. Chem. Soc., 1967, 89, 1123–1126; (e) D. A. Evans, W. L.
Scott and L. K. Truesdale, Tetrahedron Lett., 1972, 13, 121–124; (f) P.
Martinez-Fresneda and M. Vaultier, Tetrahedron Lett., 1989, 30, 2929–
2932; (g) K. Narasaka and I. Yamamoto, Tetrahedron, 1992, 48, 5743–
5754; (h) C. Rasset and M. Vaultier, Tetrahedron, 1994, 50, 3397–3406;
(i) J. D. Bonk and M. A. Avery, Tetrahedron: Asymmetry, 1997, 8,
1149–1152; (j) G. Lorvelec and M. Vaultier, Tetrahedron Lett., 1998,
39, 5185–5188; (k) R. A. Batey, A. N. Thadani and A. J. Lough, J. Am.
Chem. Soc., 1999, 121, 450–451.
5 (a) P. Lidstro¨m, J. Tierney, B. Wathey and J. Westman, Tetrahedron,
2001, 57, 9225–9283; (b) C. O. Kappe, Angew. Chem., Int. Ed., 2004,
43, 6250–6284; (c) C. O. Kappe and D. Dallinger, Mol. Diversity, 2009,
13, 71–193; (d) S. Caddick and R. Fitzmaurice, Tetrahedron, 2009, 65,
3325–3355; (e) Microwaves in Organic Synthesis, ed. A. Loupy, Wiley-
VCH: Weinheim, 2002.
6 (a) A. P. Lightfoot, G. Maw, C. Thirsk, S. J. R. Twiddle and A.
Whiting, Tetrahedron Lett., 2003, 44, 7645–7648; (b) A. P. Lightfoot,
S. J. R. Twiddle and A. Whiting, Org. Biomol. Chem., 2005, 3, 3167–
3172.
4.2, J3x,4 = 4.2 Hz, 1H, H-3x), 1.25–1.06 (m, 15H, H-3n, H-7 and
H-9), 0.68 (ddd, J2,3n = 9.7, J2,3x = 4.9, J1,2 = 1.3 Hz, 1H, H-2).
13C NMR (75 MHz; CDCl3) d: 137.0 (CH, C-6), 134.2 (CH, C-5),
82.8 (2C, C-8), 47.4 (CH2, C-7), 44.0 (CH, C-1), 42.2 (CH, C-4),
27.6 (CH2, C-3), 24.6 (4CH3, C-9), C-2 signal missing. 11B NMR
(96 MHz; CDCl3) d: 34.1.
Typical procedure for the tandem microwave-assisted Diels–Alder
reaction of vinylboronates - oxidation (Table 2). Synthesis of
Bicyclo[2.2.1]hept-5-en-2-ol (4a)12
The microwave-assisted Diels–Alder reaction between 1b and 2a
was performed as described above. Upon completion, the reaction
mixture was diluted with THF (3 mL), and transferred to a
25 mL round-bottom flask. After the addition of Et3N (1 mL)
◦
the solution was cooled to 0 C and treated alternately with 3 N
NaOH (3 mL) and 30% H2O2 (3 mL) under argon atmosphere,
and then allowed to warm to room temperature and stirred
overnight. The reaction mixture was diluted with water (10 mL)
and extracted with Et2O (3 ¥ 15 mL). The combined organic
layers were washed with saturated NH4Cl (15 mL) and brine
(15 mL) and dried over anhydrous Na2SO4. The solvent was
removed under reduced pressure at 0 ◦C, and the crude was purified
by column chromatography (pentane–Et2O) to afford alcohol 4a
(92%, 48.3 mg, endo/exo 37 : 63) with NMR spectra identical to
the commercial material.
7 Several reactions were run to determine the optimal reaction time and
temperature for each diene.
8 J. Sauer and R. Sustmann, Angew. Chem., Int. Ed. Engl., 1980, 19,
779–807.
9 The structure of the products were determined by a combination of
spectroscopic methods. See the Supporting Information.
10 Conditions for DA reactions are the same as reported in Table 1.
11 Boronates 3b, 3f and 3i have been previously synthezised by Diels–
Alder reactions of dichlorovinylborane and the corresponding dienes
followed by hydrolysis and esterification with pinacol: N. Noiret, A.
Youssofi, B. Carboni and M. Vaultier, J. Chem. Soc., Chem. Commun.,
1992, 1105–1107.
12 Alcohols 4a–4f have been previously synthezised by other methods,
including the Diels–Alder reactions of vinylboranes and the corre-
sponding dienes followed by oxidation: (a) D. A. Singleton, J. P.
Martinez, J. V. Watson and G. M. Ndip, Tetrahedron, 1992, 48, 5831–
5838; (b) D. A. Singleton, J. P. Martinez and G. M. Ndip, J. Org.
Chem., 1992, 57, 5768–5771; (c) M. Zaidlewicz, J. R. Binkul and W.
Soko´l, J. Organomet. Chem., 1999, 580, 354–362.
Acknowledgements
We thank CONICET, U.N.R. and ANPCyT for financial support.
A.M.S. thanks CONICET for the award of a fellowship. P.L.P.
thanks ANPCyT for the award of a fellowship.
Notes and references
1 Boronic Acids, ed. D. G. Hall, Wiley-VCH: Weinheim, 2005.
2 G. Hilt and P. Bolze, Synthesis, 2005, 2091–2115.
3 (a) J. E. Moore, M. York and J. P. A. Harrity, Synlett, 2005, 860–862;
(b) M. D. Helm, J. E. Moore, A. Plant and J. P. A. Harrity, Angew.
Chem., Int. Ed., 2005, 44, 3889–3892; (c) P. M. Delaney, J. E. Moore
and J. P. A. Harrity, Chem. Commun., 2006, 3323–3325; (d) M. D.
Helm, A. Plant and J. P. A. Harrity, Org. Biomol. Chem., 2006, 4,
4278–4280; (e) E. Gomez-Bengoa, M. D. Helm, A. Plant and J. P. A.
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