Suppression effect of the Pd/C-catalyzed hydrogenolysis of a phenolic benzyl protective group by the addition of nitrogen-containing bases

Tetrahedron Letters

Volumn 39, Issue 39, 1998, Pages 7127-7130

  Sajiki, Hironao ^a   Kuno, Hiroko ^a   Hirota, Kosaku ^a  

^a GIFU PHARMACEUTICAL UNIVERSITY   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

ARTICLE; CONFORMATIONAL TRANSITION; HYDROGENATION; STRUCTURE ANALYSIS; SYNTHESIS;

EID: 0032563980     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(98)01514-7     Document Type: Article

References (16)

1. [1] Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis, John Wiley & Sons, Inc., New York, 2nd ed., 1991, pp. 47-53 and 156-158.
2. [2] For reviews, see: a) Rylander, P. N. Hydrogenation Methods, Academic Press, New York, 1985, pp. 157-163;
3. b) Idem., Catalytic Hydrogenation in Organic Synthesis, Academic Press, New York, 1979, pp. 271-279;
4. c) Freifelder, M. Practical Catalytic Hydrogenation Techniques and Applications, Wiley-Interscience, New York, 1971, pp. 398-413 and 428-440.
5. [3] The best known of the chemoselective catalysts is the Lindlar catalyst, Pd-Pb-on-calcium carbonate, which has been used successfully for the selective hydrogenation of acetylenes to olefins, and the hydrogenation of acid chlorides to aldehydes, see: ref. [2]-a) pp. 53-65 and 153-156.
6. [4] Sajiki, H. Tetrahedron Lett. 1995, 36, 3465-3468.
7. [5] Czech and Bartsch also reported the inhibition of Pd/C-catalyzed hydrogenolysis of 11-(benzyloxy)-1-undecene using n-butylamine as an additive, see: Czech, B. P.; Bartsch, R. A. J. Org. Chem. 1984, 49, 4076-4078.
8. [5,11] However, phenolic O-benzyl ether in spite of the presence of intramolecular amine was debenzylated, see: a) Forbes, E. J. J. Chem. Soc. 1955, 3926-3932.
9. b) Kirby, G. W.; Tiwari, H. P. J. Chem. Soc. (C) 1966, 676-682.
10. [7] Sajiki, H; Kuno, H.; Hirota, K. Tetrahedron Lett. 1997, 38, 399-402.
11. [8] These reactions were followed by a TLC scanner (Shimadzu CS-9000). All reactions were carried out at ordinary pressure (balloon) and temperature (ca. 20 °C) with 5% Pd/C (10 weight%) in MeOH in the presence of 0.5 equiv. of amine or nitrogen-containing base .
12. [9] 1,10-Phenanthroline could also be partially hydrogenated under the reaction conditions.
13. 4) and concentrated to provide the product without any by-product. The resulting product was purified by flash silica gel column chromatography, if necessary.
14. [11] For examples, a) Pennings, M. L. M.; Reinhoudt, D. N. J. Org. Chem. 1983, 48, 4043-4048.
15. b) Fleet, G. W.; Smith, P. W. Tetrahedron Lett. 1985, 26, 1469-1472.
16. [12] If the product possesses an amino moiety (Table 2, entries 1, 2 and 7), the organic layer was washed with only brine. After concentration, the residue was purified by flash silica gel column chromatography to remove 2,2′-dipyridyl.