A Practical and Highly Chemoselective Hydrogenation of Aldehydes with a Copper Catalyst

Abstract

A practical hydrogenation of aldehydes mediated by an inexpensive and easily available base metal, copper, is reported. A copper complex associated with 1,4-bis(diphenylphosphino)butane (DPPB) hydrogenates α,β-unsaturated aldehydes in a highly chemoselective fashion to give allylic alcohols with improved catalytic productivities. The reaction system was also effective for the conversion of simple aldehydes to the corresponding alcohols.

Key words

hydrogenation - aldehydes - copper - homogeneous catalysis - chemoselectivity

References and Notes

• 1a Chapuis C. Jacoby D. Appl. Catal., A  2001,  221:  93 
• 1b Common Fragrance and Flavor Materials   Surburg H. Panten J. Wiley-VCH; Weinheim: 2006. 
• 1c Saudan LA. Acc. Chem. Res.  2007,  40:  1309 
• 2 Gallezot P. Richard D. Catal. Rev.  1998,  40:  81 
• 3 Recent review: Clarke ML. Roff GJ. Handbook of Homogeneous Hydrogenation   Vol. 1:  de Vries JG. Elsevier CJ. Wiley-VCH; Weinheim: 2007.  Chap. 15. p.413-454  
• 4a Grosselin JM. Mercier C. Allmang G. Glass F. Organometallics  1991,  10:  2126 ; and references cited therein
• 4b Milone C. Tropeano ML. Gulino G. Neri G. Ingoglia NR. Galvagno S. Chem. Commun.  2002,  868 
• 5a Ohkuma T. Ooka H. Ikariya T. Noyori R. J. Am. Chem. Soc.  1995,  117:  10417 
• 5b Noyori R. Ohkuma T. Angew. Chem Int. Ed.  2001,  40:  40 
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• 6b Chen J.-X. Daeuble JF. Stryker JM. Tetrahedron  2000,  56:  2789 
• 8 Shimizu H. Igarashi D. Kuriyama W. Yusa Y. Sayo N. Saito T. Org. Lett.  2007,  9:  1655 
• 9 [Cu(NO₃)(PPh₃)₂] can be prepared from Cu(NO₃)₂˙3H₂O and Ph₃P. See: Gysling HJ. Inorg. Chem.  1979,  19:  92 

7

Our attempt to hydrogenate (-)-4-(prop-1-en-2-yl)cyclo-hexen-1-carbaldehyde [(-)-perilaldehyde] at S/C = 500
with the condition described in ref. 6b, resulted in trace conversion. The reaction reportedly completed at S/C = 20, which was reproduced by us.

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Representative Procedure (Table 1, Entry 1)
To a 100 mL stainless steel autoclave equipped with a glass inner lining and a Teflon-coated stirring bar were added [Cu(NO₃)(PPh₃)₂] (11.7 mg, 0.018 mmol) and DPPB (7.7 mg, 0.018 mmol). The atmosphere was replaced with N₂, and an EtOH solution (0.03 M) of NaOH (6.0 mL, 0.18 mmol) and (E)-2-methyl-3-phenylprop-2-enal (E/Z = 99:1; 1.26 mL, 9.0 mmol) were then added. Hydrogen gas was initially introduced into the autoclave at a pressure of 1.0 MPa before being reduced to 0.1 MPa by carefully releasing the stop valve. After this procedure was repeated three times, H₂ was introduced at 5.0 MPa and the solution was stirred at 50 ˚C for 16 h. Silica gel chromatography (Et₂O-hexane = 1:1) after removal of the solvent gave (E)-2-methyl-3-phenyl-
prop-2-en-1-ol (1.32 g, 99%, E/Z = 99:1).