10.1021/ol202800k r 2011 American Chemical Society Published on Web 11/15/2011 ORGANIC LETTERS 2011 Vol. 13, No. 24 6504–6507 Selenium-Catalyzed Regioselective Cyclization of Unsaturated Carboxylic Acids Using Hypervalent Iodine Oxidants Fateh V. Singh and Thomas Wirth* School of Chemistry, Cardiff University, Park Place, Cardiff CF10 3AT, U.K. wirth@cf.ac.uk Received October 18, 2011 ABSTRACT A new and convenient selenium-catalyzed regioselective cyclization of γ,δ-unsaturated carboxylic acids to the corresponding 3,6-dihydro-2H- pyran-2-ones is described. The cyclization products have been obtained in good to excellent yields using diphenyl diselenide as a catalyst and [bis(trifluoroacetoxy)iodo]benzene as a stoichiometric oxidant. In the past few decades, organoselenium chemistry has been developed into an important tool in synthetic organic chemistry. Several organoselenium reagents have been employed in various useful synthetic transformations such as selenenylations, selenocyclizations, selenoxide elimi- nations, and 2,3-sigmatropic rearrangements. 1 Recently, organoselenium reagents have been used catalytically in various synthetic transformations such as oxidation of alcohols, 2 olefins, 3 and carbonyl compounds; 4 elimination reactions of diols; 5 DielsÀAlder reactions; 6 and BaylisÀ Hillman 7 and radical chain reactions. 8 Recently, we have reported the selenium-catalyzed synthesis of butenolides 9 and isocoumarins 10 by cyclization of β,γ-butenoic acids and stilbene carboxylic acids, respectively. The cyclization of γ,δ-unsaturated pentenoic acids with selenium reagents as catalysts is still unexplored. Our target was to achieve the synthesis of 2H-pyran-2-ones by cyclization of γ,δ- unsaturated pentenoic acids using selenium reagents as a catalyst. The 2H-pyran-2-one scaffolds are known for various biological properties, and this structural motif is found in several natural products. 11 In addition, the (1) (a) Organoselenium Chemistry; Wirth, T., Ed.; Wiley-VCH: Weinheim, 2011. (b) Santi, C.; Santoro, S.; Battistelli, B. Curr. Org. Chem. 2010, 14, 2442. (c) Freudendahl, D. M.; Shahzad, S. A.; Wirth, T. Eur. J. Org. Chem. 2009, 1649–1664. (d) Freudendahl, D. M.; Santoro, S.; Shahzad, S. A.; Santi, C.; Wirth, T. Angew. Chem. 2009, 121, 8559–8562. Angew. Chem., Int. Ed. 2009, 48, 8409–8411. (e) Browne, D. M.; Wirth, T. Curr. Org. Chem. 2006, 10, 1893–1903. (f) Wirth, T. Angew. Chem. 2000, 112, 3890–3900. Angew. Chem., Int. Ed. 2000, 39, 3740–3751. (g) Wirth, T. Tetrahedron 1999, 55, 1–28. (2) (a) Onami, T.; Ikeda, M.; Woodard, S. S. Bull. Chem. Soc. Jpn. 1996, 69, 3601–3605. (b) Ehara, H.; Noguchi, M.; Sayama, S.; Onami, T. J. Chem. Soc., Perkin Trans. 1 2000, 1429–1431. (c) van der Toorn, J. C.; Kemperman, G.; Sheldon, R. A.; Arends, I. W. C. E. J. Org. Chem. 2009, 74, 3085–3089. (d) Singh, P.; Singh, A. K. Eur. J. Inorg. Chem. 2010, 4187–4195. (3) (a) Betzemeier, B.; Lhermitte, F.; Knochel, P. Synlett 1999, 489– 491. (b) Goodman, M. A.; Detty, M. R. Synlett 2006, 1100–1104. (c) Garcia-Marin, H.; van der Toorn, J. C.; Mayoral, J. A.; Garcia, J. I.; Arends, I. W. C. E. Green Chem. 2009, 11, 1605–1609. (d) Gogoi, P.; Sharma, S. D.; Konwar, D. Lett. Org. Chem. 2007, 4, 249–252. (e) Santoro, S.; Santi, C.; Sabatini, M.; Testaferri, L.; Tiecco, M. Adv. Synth. Catal. 2008, 350, 2881–2884. (f) Brodsky, B. H.; Du Bois, J. J. Am. Chem. Soc. 2005, 127, 15391–15393. (g) Carrera, I.; Brovetto, M. C.; Seoane, G. A. Tetrahedron Lett. 2006, 47, 7849–7852. (4) (a) Brink, G.; Vis, J.-M.; Arends, I. W. C. E.; Sheldon, R. A. J. Org. Chem. 2001, 66, 2429–2433. (b) Miyake, Y.; Nishibayashi, Y.; Uemura, S. Bull. Chem. Soc. Jpn. 2002, 75, 2233–2237. (c) Ichikawa, H.; Usami, Y.; Arimoto, M. Tetrahedron Lett. 2005, 46, 8665–8668. (d) W ojtowicz, H.; Brzaszcz, M.; Kloc, K.; Mlochowski, J. Tetrahedron 2001, 57, 9743–9748. (5) Crich, D.; Neelamkavil, S.; Sartillo-Piscil, F. Org. Lett. 2000, 2, 4029–4031. (6) Lenardao, E. J.; Mendes, S. R.; Ferreira, P. C.; Perin, G.; Silveira, C. C.; Jacob, R. G. Tetrahedron Lett. 2006, 47, 7439–7442. (7) Lenardao, E. J.; Feijo, J. O.; Thurow, S.; Perin, G.; Jacob, R. G.; Silveira, C. C. Tetrahedron Lett. 2009, 50, 5215–5217. (8) (a) Clive, D. L. J.; Pham, M. P.; Subedi, R. J. Am. Chem. Soc. 2007, 129, 2713–2717. (b) Crich, D.; Sannigrahi, M. Tetrahedron 2002, 58, 3319–3322. (c) Crich, D.; Rumthao, S. Tetrahedron 2004, 60, 1513– 1516. (d) Crich, D.; Patel, M. Org. Lett. 2005, 7, 3625–3628. (9) (a) Browne, D. M.; Niyomura, O.; Wirth, T. Org. Lett. 2007, 9, 3169–3171. (b) Browne, D. M.; Niyomura, O.; Wirth, T. Phosphorus Sulfur 2008, 183, 1026–1035. (10) Shahzad, S. A.; Venin, C.; Wirth, T. Eur. J. Org. Chem. 2010, 3465–3472. (11) Goel, A.; Ram, V. J. Tetrahedron 2010, 65, 7865–7913.