Chemoselective reductions with sodium borohydride. Aldehydes vs. ketones

Synthetic Communications

Volumn 18, Issue 16-17, 1988, Pages 1927-1933

  Ward, Dale E ^a   Rhee, Chung K ^a  

^a UNIVERSITY OF SASKATCHEWAN   (Canada)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0347366141     PISSN: 00397911     EISSN: 15322432     Source Type: Journal    
DOI: 10.1080/00397918808068259     Document Type: Article

References (10)

1. 4- resin) Yoon, N.M.; Park, K.B.; Gyoung, Y.S.; ibid., 1983, 24, 5367 - 70; (w) (BH3/pyr/AI203) Babler, J.H.; Sarussi, S.J.;J. Org. Chem., 1983, 48, 4416 - 19; (x) (8-oxyquinoline dihydroboronite/BF3-Et20) Kim, S.; Kang, H.J.; Yang, S.;Tetrahedron Lett., 1984, 25, 2985-86; idem., Bull. Korean Chem. Soc., 1984, 5, 240-44; (y) (NaBH4/CeCl3/DMSO) Adams, C.;Syn. Comm., 1984, 14, 1349-53; (z) (Et4N(μ-mo2(co)i0) Gibson, D.H.; El-Omrani, Y.S.;Organometalics, 1985, 4, 1473-75; (aa) (HCOOH/R3N/RuCI2(Ph3P)3) Khai, B.T.; Arcelli, A.;Tetrahedron Lett., 1985, 26, 3365-68; (bb) (KPh3BH) Yoon, N.M.; Kim, K.E.; Kang, J.; J. Org. Chem., 1986, 51, 226-29; (cc) (NaBH4/Bu4NBr) Rao, C.S.; Deshmukh, A.A.; Patel, B.J.;Indian J. Chem., 1986, 25b, 626-29; (dd) (TMSCI/Ni2B) Borbaruah, M.; Barua, N.C.; Sharma, R.P.; Tetrahedron Lett., 1987, 28, 5741–42.
2. Brown, H.C.; Krishnamurthy, S.; Tetrahedron, 1979, 35, 567; (b) Walker, E.R.H.; Chem. Soc. Rev., 1976, 5, 23.
3. Ward, D.E.; Rhee, C.K.; Zoghaib, W.M.; Tetrahedron Lett., 1987,29, 517–519.
4. 4 for selective reduction of aldehydes in the presence of ketones has been reported (ref. 1c) in 2 examples. The method uses 1 eq. of hydride in ethanol at room temperature. This method gives poor selectivity (70%) with 4-methylcyclohexanone/hexanal.
5. Selectivity as high as 90% has been reported in few cases (ref 1i,1k,1s,1z,1bb).
6. The use of undistilled acetaldehyde results in much poorer selectivity presumably due to the presence of acetic acid. The presence of acetic acid dramatically increases the rate of reduction (for an example see ref. 3).
7. Brown, H.C.; Ichikawa, K.; Tetrahedron, 1957, 1, 221.
8. The amount of alcohol in the solvent is directly related to the rate of reduction. Increased amounts gave poorer selectivity while reduced amounts gave poorer conversion (during 1h).
9. 2at -78° C for 1 h (selectivity-85%)
10. 1k,1s.