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Bhowmick, M.; Karmakar, A. Tetrahedron Lett. 2005, 46, 3073–3077; (c) Yeung,
Y.-Y.; Gao, X.; Corey, E. J. J. Am. Chem. Soc. 2006, 128, 9644–9645; (d) Ahmad, S.
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No work-up was required and products were purified by silica gel
chromatography. cis-Alkenes (Table 2, entries 1 and 3) participate
in the cyclization, generating product in high yield with >20:1 dia-
stereoselectivity.11 A terminal alkene (entry 2) reacts readily to
give a 51% yield of iodotetrahydrofuran 4. The moderate yield is
attributed to product volatility since the 1H NMR spectrum of an
unpurified sample showed clean product formation. A trans-alkene
also undergoes stereospecific iodocyclization in excellent yield
(entry 4). Iodide 8 was isolated as a 7:1 mixture of inseparable
compounds, which is attributed to formation of the 6-endo cycliza-
tion product.
We were delighted to find that tetrahydropyran formation was
also possible. The reactions were slower than 5-membered ring
formation, so catalyst loading was increased to 5 mol % and reac-
tion time was extended to 6 h. Terminal alkene 9 cyclized to give
tetrahydropyran 10 in moderate yield (Table 2, entry 5). Again,
product volatility played a role in isolation. The trans- and cis-al-
kenes cyclized to give a single stereoisomer of tetrahydropyran
in good yield (entries 6 and 7).
3. For
a review on recent methods for the stereoselective synthesis of
tetrahydrofurans, see: Wolfe, J. P.; Hay, M. B. Tetrahedron 2007, 63,
261–290.
4. (a) El-Qisairi, A.; Hamed, O.; Henry, P. M. J. Org. Chem. 1998, 63, 2790–2791;
(b) Kang, S. H.; Lee, S. B.; Park, C. M. J. Am. Chem. Soc. 2003, 125, 15748–15749.
5. (a) Dick, A. R.; Hull, K. L.; Sanford, M. S. J. Am. Chem. Soc. 2004, 126, 2300–2301;
(b) Kalyani, D.; Dick, A. R.; Anani, W. Q.; Sanford, M. S. Org. Lett. 2006, 8, 2523–
2526.
6. (a) Manzoni, M. R.; Zabawa, T. P.; Kasi, D.; Chemler, S. R. Organometallics 2004,
23, 5618–5621; (b) Alexanian, E. J.; Lee, C.; Sorensen, E. J. J. Am. Chem. Soc. 2005,
127, 7690–7691; (c) Streuff, J.; Hövelmann, C. H.; Nieger, M.; Muñiz, K. J. Am.
Chem. Soc. 2005, 127, 14586–14587; (d) Liu, G.; Stahl, S. S. J. Am. Chem. Soc.
2006, 128, 7179–7181.
7. Michael, F. E.; Sibbald, P. A.; Cochran, B. M. Org. Lett. 2008, 10, 793–796.
8. Desai, L. V.; Sanford, M. S. Angew. Chem., Int. Ed. 2007, 46, 5737–5740.
9. (a) Faul, M. M.; Huff, B. E. Chem. Rev. 2000, 100, 2407–2474; (b) Kang, E. J.; Lee,
E. Chem. Rev. 2005, 105, 4348–4378; For a review on halogenated natural
products, see: Gribble, G. W. Acc. Chem. Res. 1998, 31, 141–152.
10. General procedure: An oven-dried vial containing a Teflon-coated stir bar was
charged with 7.3 mg (0.009 mmol) of dichloro[1,2-bis(diphenylphos-
phino)ferrocene]palladium(II) dichloromethane adduct on the benchtop. The
vial was purged with argon, and the solid was suspended in 1.5 mL of dry
toluene. N-Iodosuccinimide (81 mg, 0.36 mmol) was transferred as a solid to
the vial. Fifty–five microliters (0.3 mmol) of cis-4-decen-1-ol (5) were added to
the suspension via syringe. The mixture was stirred at room temperature
under argon for 90 min. After this time, the suspension was loaded directly
In summary, we have developed a palladium-catalyzed intra-
molecular iodoetherification reaction. Incorporation of diphos-
phine ligands is promising for the development of a catalytic,
enantioselective process. Further investigation into catalysts for
enantiocontrol and the reaction mechanism are underway.
onto
a silica gel column. The crude mixture was purified by flash
chromatography with 50 mL of hexanes followed by 15:1 hexanes/ether.
Tetrahydrofuran 6 (78 mg, 92%) was isolated as a clear oil. 1H NMR (400 MHz,
CDCl3): d 4.13–4.08 (ddd, 1H), 4.00–3.94 (dt, 1H), 3.87–3.81 (ddd, 1H), 3.77–
3.72 (ddd, 1H), 2.12–1.82 (m, 4H), 1.77–1.55 (m, 3H), 1.47–1.21 (m, 5H), 0.90
(t, 3H). 13C NMR (100 MHz, CDCl3): d 82.4, 68.9, 42.8, 36.3, 31.0, 30.8, 29.4,
26.2, 22.5, 14.0.
Acknowledgments
We would like to thank Research Corporation (Cottrell College
Science Award) and UNCW (Cahill Award) for funding.
11. Products 2, 4, 6, and 10 displayed characterization data identical to
literature values. Major diastereomer assignment was based on products
References and notes
2
and 6.
1. (a) Rodriguez, J.; Dulcère, J.-P. Synthesis 1993, 1177–1205; (b) da Silva, F. M.;
Junior, J. J.; de Mattos, M. C. S. Curr. Org. Synth. 2005, 2, 393–414.