Modulation of the Cs2CO3-promoted catalytic amination by a crown ether

For recent reviews, see: (a) Yang, B. H.; Buchwald, S. L. J. Organomet. Chem. 1999, 576, 125. (b) Hartwig, J. F. Angew. Chem., Int. Ed. Engl. 1998, 37, 2046. (c) Wolfe, J. P.; Wagaw, S.; Marcoux, J.-F.; Buchwald, S. L. Acc. Chem. Res. 1998, 31, 805. For very recent results, see: (a) Wolfe, J. P.; Buchwald, S. L. J. Org. Chem. 2000, 65, 1144. (b) Wolfe, J. P.; Tomori, H.; Sadighi, J. P.; Yin, J.; Buchwald, S. L. J. Org. Chem. 2000, 65, 1158. (c) Rivas, F. M.; Riaz, U.; Diver, S. T. Tetrahedron: Asymmetry 2000, 11, 1703. As a review, see: Sturmer, R. Angew. Chem., Int. Ed. Engl. 1999, 87, 3307. For recent topics, see: (a) Yin, J.; Buchwald, S. L. Org. Lett. 2000, 2, 1101. (b) Bolm, C.; Hildebrand, J. P. J. Org. Chem. 2000, 65, 169 and references cited therein (15). (c) Zhang, C.; Huang, J.; Trudell, M. L.; Nolan, S. P. J. Org. Chem. 1999, 64, 3804. (d) Hennings, D. D.; Iwama, T.; Rawal, V. H. Organic Lett. 1999, 1, 1205. (e) Zhang, C; Trudell, M. L. Tetrahedron Lett. 2000, 41, 595. Watanabe, 2000, Tetrahedron Lett., 41, 481, 10.1016/S0040-4039(99)02096-1 Prashad, 2000, J. Org. Chem., 65, 1158, 10.1021/jo991949a Torisawa, 1997, Bioorg. Med. Chem. Lett., 7, 1821, 10.1016/S0960-894X(97)00315-6 (a) Oshiro, Y.; Sato, S.; Kurahashi, N.; Tanaka, T.; Kikuchi, T.; Tottori, K.; Uwahodo, Y.; Nishi, T. J. Med. Chem. 1998, 41, 658. (b) Morita, S.; Kitano, K.; Matsubara, J.; Ohtani, T.; Kawano, Y.; Otsubo, K.; Uchida, M. Tetrahedron 1998, 54, 4811. Oshiro, 2000, J. Med. Chem., 43, 177, 10.1021/jm980333v Wolfe, 1997, J. Org. Chem., 62, 6066, 10.1021/jo970876x Better solubility of Cs salt than Na salt might be a key factor for the interaction with Crown ether and hence the improvement of product yield. Some stabilization of arylpalladium intermediate by a Crown ether was proposed in ref 12a. We also observed effective interaction in Cs/Crown combination over K/Crown system in the reaction of boiling toluene; see ref 12b. For some interactions between Crown ether and metals, see for example: (a) Pd/Zn/18-Crown-6 combination: Venkatraman, S.; Li, C.-J. Tetrahedron Lett., 2000, 41, 4831. (b) CsOAc/18-Crown-6 combination: Torisawa, Y.; Okabe, H.; Ikegami, S. Chem. Lett. 1984, 1555. (c) Izatt, R. M.; Bradshaw, J. S.; Nielsen, S. A.; Lamb, J. D.; Christensen, J. J. Chem. Rev. 1985, 85, 271. Torisawa, 2000, Bioorg. Med. Chem. Lett., 10, 2493, 10.1016/S0960-894X(00)00501-1 Witulski, B. Synlett 1999, 1223–1226, and references cited therein. We selected here 18-Crown-6 as a representative Crown ether based on our previous study (ref 12b).