Metal catalyst-free by design. The synthesis of amides from alkyl iodides, carbon monoxide and amines by a hybrid radical/ionic reaction

Abstract

Amides can be synthesized from alkyl iodides and amines in the presence of CO (20–25 atm), without using transition metal catalyst; the radical cascade is initiated thermally using AIBN and allyltributyltin.

References

1. For recent progress in the efficient recovery of catalysts including fluorous biphasic systems, see J. A. Gladysz, Science, 1994, 266, 55; I. T. Horváth and J. Rábai, Science, 1994, 266, 72; J. J. J. Juliette, I. T. Horváth and J. A. Gladysz, Angew. Chem., Int. Ed. Engl., 1997, 36, 1610 Also see a related review: D. P. Curran, Angew. Chem., Int. Ed., 1998, 37, 1174.
2. K. Nagahara, I. Ryu, M. Komatsu and N. Sonoda, J. Am. Chem. Soc., 1997, 119, 5465.
3. General procedure: A magnetic stirring bar, AIBN (0.3 mmol), hexane (0.5 ml), allyltributyltin (0.1 mmol), alkyl iodide 1a(1 mmol), triethylamine (1.3 mmol) and amine (1.2 mmol) were placed in a 50 ml stainless steel autoclave with a glass liner. The autoclave was closed, purged twice with CO, pressurized with 25 atm of CO and then heated with stirring at 80 °C for 8 h. Excess CO was discharged at room temperature. Washing the crude mixture with MeCN (10 ml) followed by precipitation of ammonium salts in Et₂O (40 ml), filtration, evaporation of filtrate and column chromatography on silica gel gave pure amide 2.
4. Rapid decarbonylation rates (10⁵ to 10⁶ s^–1 at room temp.) of pivaloyl radical are known, see: Y. P. Tsentalovich and H. Fischer, J. Chem. Soc., Perkin Trans. 2, 1994, 729; C. E. Brown, A. G. Neville, D. M. Rayner, K. U. Ingold and L. Lusztyk, Aust. J. Chem., 1995, 48, 363; C. Chatgilialoglu, C. Ferreri, M. Lucarini, P. Pedrielli and G. F. Pedulli, Organometallics, 1995, 14, 2672.
5. I. Ryu and N. Sonoda, Angew. Chem., Int. Ed. Engl., 1996, 35, 1050.
6. P. Renaud, E. Lacôte and L. Quaranta, Tetrahedron Lett., 1998, 39, 2123.
7. Reaction of primary alkyl iodides under thermal initiation conditions suffers from direct aminolysis.
8. For examples of amide synthesis by catalytic carbonylation, see A. Schoenberg and R. F. Heck, J. Org. Chem., 1974, 39, 3327; T. Kobayashi and M. Tanaka, J. Organomet. Chem., 1982, 231, C12; T. Kobayashi and M. Tanaka, J. Organomet. Chem., 1982, 233, C64; F. Ozawa, H. Soyama, T. Yamamoto and A. Yamamoto, Tetrahedron Lett., 1982, 23, 3383; T. Kondo, Y. Sone, Y. Tsuji and Y. Watanabe, J. Organomet. Chem., 1994, 473, 163 Also see a related review: A. Yamamoto, Bull. Chem. Soc. Jpn., 1995, 68, 433.