Reduction of Undecylinic acid to Undecanoic acid using NaBH4-Ni in water; Undecanoic acid
SyntheticPage 565
DOI:
10.1039/SP565
Submitted Jul 17, 2012, published Jul 20, 2012
Ramesha Ramakrishna (
ramesha63@hotmail.com)
A contribution from
ramesha
Chemicals Used
Undecylinic acid -commercial, Purity 98%
Sodium borohydride, Aldrich
Sodium hydroxide, commercial
Hydrochloric acid, 35%, commercial
Toluene, commercial, min 99%
Raney-Nickel, commercial
Procedure
In a 3 Lt four necked round bottom flask equipped with a mechanical stirrer, 250 mL dropping funnel, thermometer and inlet port open to the atmosphere on a water bath was charged under stirring distilled water(1200 mL), sodium hydroxide (88 g, 2.2 mol), undecylinic acid acid (368 g, 2 mol), activated W-6 Raney nickel (70 g wet in water) and stirred for 10 min. The reaction mass was cooled to about 25-30oC . To the above aqueous solution, freshly prepared Sodium borohydride solution (21 g, 0.55 mol, in 1% aqueous NaOH solution 100 mL) was added drop wise through dropping funnel over a period of 45-60 min. The reaction mixture was stirred for additional 60 min at 25-30 oC. And then further stirred at 40-45oC for 1 h. The reaction flask was removed from the water bath, and the mixture cooled to a room temperature. Then solution was filtered through a Buchner funnel and the W-6 Raney rinsed with distilled water (100 mL, Raney nickel thus obtained is pyrophoric and should be kept under water immediately). The filtrate was acidified with concentrated Hydrochloric acid to pH-2. The resulting oily layer was extracted with toluene (1 Lt twice) and washed with water 500 mL (2 times). The toluene layer thus obtained was concentrated under reduced pressure to get Undecanoic acid 353 g (95%).Which is normally pure by NMR.
Author's Comments
1. Sodium borohydride, normally known for carbonyl reduction, effectively used for hydrogenation in this procedure.
2. All the 4 hydrogen of sodium borohydride is consumed in the procedure. Therefore only ~0.25 equivalent of sodium borohydride is required for the reduction.
3. Raney Nickel is pyrophoric when dry. Care should be taken while handling Raney Nickel-it.
4. Sodium borohydride can give rise to flamable hydrogen gas if it comes in contact with acidic reagents. Therefore it should be added to alkaline aqueous solution (1 g sodium hydroxide in 100 mL water). The whole reaction medium should be maintained at alkaline pH.
5. This reaction is very general and can be used for any substrates which can be dissolved in water by converting into their sodium salt.
6. This is the best alternate procedure to hydrogenation. Hydrogenation can be planned in 1-2 kg batch with out the requirement of hydrogenator.
Data
Viscous liquid. IR (neat):1702, 3205 cm-1 . 1H NMR (200 MHz, CDCl3): δ 0.87 – 2.33(2m, 21H); 13C NMR (50 MHz, CDCl3): δ 14.0, 22.6, 25.1, 29.3, 29.5, 29.6, 31.9, 34.4, 35.3, 37.3, 180.0.
Lead Reference
Gopal Krishna Rao a , Narendra B. Gowda b & Ramesha A.Ramakrishna Synthetic Communication. 2012, 42, 893-904
dx.doi.org/10.1080/00397911.2010.533239
Other References
Brown, C. A. J. Org. Chem. 1970, 35, 1900-1904
http://dx.doi.org/10.1021/jo00831a039P. L. Cramer, W. Lee LewisJ. Am. Chem. Soc. 1930, 52, 4349-4358.
http://dx.doi.org/10.1021/ja01364a034Parshal, G. W. J. Am. Chem. Soc. 1972, 94, 8716- 8719.
http://dx.doi.org/10.1021/ja00780a013Gribble, G.W. Chem. Soc. Rev. 1998, 27, 395-404.
http://dx.doi.org/10.1039/a827395z
Supplementary Information
Proton and carbon NMR (supporting information synthetic.doc)
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Keywords: Alkanes, alkenes, carboxylic acids, Raney-nickel, reduction, sodium borohydride, undecanoic acid, Undecylinic acid
