(Hive Bee)
11-29-02 16:33
No 384596
      Ion exchange resin-borohydride
(Rated as: excellent)

Synthetic Communications, 19 (5&6), 805-811 (1989)

The reduction of alpha, beta-unsaturated nitroalkenes to nitroalkanes with borohydride supported on an ion exchange resin

Authors: Goudgaon, Wadgaonkar and Kabalka

...We wish to report that nitroalkenes are selectively reduced to nitroalkanes by borohydride supported on an ion exchange resin in MeOH at room temperature. Borohydride bound resin was prepared by stirring commercially avaliable anion exchange resin, Amberlite IRA-400 (Cl- form) with aqueous sodium borohydride solution. The reaction procedure involves the addition of borohydride ion exchange resin to a methanolic solution of the nitroalkene. The reactions are complete in 60 minutes and can be monitored by TLC (and in some cases by the disapperance of the yellow color of the nitroalkene). The product nitroalkanes are isolated by removal of the ion exchange resin by filtration and evaporatin of the filtrate under reduced pressure. The resin may be reused by rinsing the spent material with dilute hydrochloric acid followed by regeneration with aqueous sodium borohydride solution.


Borohydride bound ion exchange resin

An aqueous solution of sodium borohydride (0,5 M, 100 ml) was stirred with 10 g of wet chloride form resin (Amberlite IRA-400) for one hour. The resulting resin was washed thoroughly with distilled water until free from excess sodium borohydride. The borohydride bound exchange resin was dried in vacuo at 65C for 5 hours. The dried resin was analyzed for borohydride content by hydrogen evolution on acidification with 0,05 N HCl; the average capacity of the ion exchange resin was found to be 2,5 mmol BH4-/g of resin.

General procedure for the synthesis of nitroalkanes

The preparation of 2-(2-nitropropyl)thiophene is representative of the procedure employed. 2-(2-Nitropropenyl)thiophene (2 mmol 0,338 g) was dissolved in MeOH (40 ml) in a 100 ml Erlenmeyer flask containing a magnetic stirring bar. Borohydride supported ion exchange resin (2,2 mmol, 0,88 g) was then added at room temperature to the well stirred solution. A mildely exothermic reaction ensued with the gradual disapperance of the yellow coloration. The reaction mixture was stirred for 60 minutes at room temperature and the the resin was filtered off, washed twice with MeOH (2x10 ml). Removal of the MeOH under reduced pressure yielded 0,265 g (78%) of pure 2-(2-nitropropyl)thiophene as an oil.

Nitrocyclohexene --> Nitrocyclohexane 80%
2-Nitro-1-phenylpropene --> 2-Nitro-1-phenylpropane 81%
2-Nitro-1-(p-bromophenyl)-propene --> 2-Nitro-1-(p-bromophenyl)-propane 80%
2-Nitro-1-(3,4-diethoxyphenyl)-propene --> 2-Nitro-1-(3,4-diethoxyphenyl)-propane 83%

Catalytic hydrogenation freak
(Chief Bee)
06-01-04 07:33
No 510662
      Varma & Kabalka: Nitroalkene -BH4-> Nitroalkane
(Rated as: excellent)

Selective Reduction of Nitroalkenes with Methanolic Sodium Borohydride: A Facile Route To Nitroalkanes
Rajender S. Varma and George W. Kabalka
Synthetic Communications, 15(2), 151-155 (1985) (../rhodium/chemistry /nitroalkene2nitroalkane.v-k.nabh4.html)

α,β-Unsaturated nitroalkenes are rapidly and selectively reduced at room temperature to nitroalkanes in high yields by sodium borohydride in a tetrahydrofuran-methanol solvent system.
____ ___ __ _

The Reduction of Nitroalkenes to Nitroalkanes with Borohydride Exchange Resin
N.M. Goudgaon, P.P. Wadgaonkar and G.W. Kabalka
Synthetic Communications, 19(5-6), 805-811 (1989) (../rhodium/chemistry /nitroalkene2nitroalkane.v-k.ber.html)

Borohydride supported on an ion exchange resin selectively reduced α,β-unsaturated nitroalkenes to nitroalkanes in high yields. The isolation of pure products by simple filtration is a key feature of this method.

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