Pd/C(en)-catalyzed regioselective hydrogenolysis of terminal epoxides to secondary alcohols

Abstract

Various terminal epoxides, such as 1,2-epoxyalkanes, glycidyl ethers and glycidol, were hydrogenolyzed to give secondary alcohols with high regioselectivity using a 10% Pd/C–ethylenediamine complex as a catalyst under entirely neutral conditions.

References

1. F. A. Carey and R. J. Sundberg, Advanced Organic Chemistry, Part B, Plenum, New York, 1977; M. Bartok and K. L. Lang, The Chemistry of Heterocyclic Compounds—Small Ring Heterocycles, Part 3, ed. A. Weissberger and E. C. Taylor, Wiley, New York, 1985, p. 1 and references therein; R. Sreekumar, R. Padmakumar and P. Rugmini, Tetrahedron Lett., 1998, 39, 5151 and references therein.
2. (a) K. Sato, M. Aoki, M. Ogawa, T. Hashimoto and R. Noyori, J. Org. Chem., 1996, 61, 8310; (b) C. Coperet, H. Adolfsson and K. B. Sharpless, Chem. Commun., 1997, 1565 and references therein.
3. Selected reviews: R. C. Larock, Comprehensive Organic Transformations, VCH, New York, 1989, p. 505; M. Hudlicky, Reductions in Organic Chemistry, 2nd edn., ACS, Washington, DC, 1996, p. 113.
4. For examples: M. S. Newman, G. Underwood and M. Renoll, J. Am. Chem. Soc., 1949, 71, 3362; P. N. Rylander, Catalytic Hydrogenation in Organic Synthesis, Academic Press, New York, 1979, p. 260; P. N. Rylander, Hydrogenation Methods, Academic Press, New York, 1985, p. 137.
5. Besides the catalyst, the substrate also exerts a considerable effect on the regioselectivity (ref. 1 and 4), see also S. Torii, H. Okuno, S. Nakayasu and T. Kotani, Chem. Lett., 1989, 1975.
6. P. S. Dragovic, T. J. Prins and R. Zhou, J. Org. Chem., 1995, 66, 4922.
7. L. M. Schultze, H. H. Chapman, N. S. Louie, M. J. Postich, E. J. Prisbe, J. C. Rohloff and R. H. Yu, Tetrahedron Lett., 1998, 39, 1853.
8. H. Sajiki, K. Hattori and K. Hirota, J. Org. Chem., 1998, 63, 7990.
9. The preparation of 10% Pd/C(en) catalyst: (ref. 8): A suspension of 10% Pd/C (1.50 g, 1.40 mmol as Pd metal) and ethylenediamine (6.8 ml, 100.80 mmol) in MeOH (60 ml) under a rigorous argon atmosphere was stirred for 48 h at ambient temperature. The solid was filtered, washed vigorously with MeOH (20 ml × 5) and Et₂O (20 ml × 2), and dried under a vacuum pump at room temperature for 48 h to give the 10% Pd/C(en)(Found: C, 74.10; H, 2.64; N, 3.01%).
10. H. Sajiki, K. Hattori and K. Hirota, J. Chem. Soc., Perkin Trans. 1, 1998, 4043.
11. By use of EtOH instead of MeOH as a solvent, styrene oxide could also be converted to an 87 : 13 mixture of phenethyl alcohol (3 R = Ph) and 1-phenylethylene glycol monoethyl ether.