I have to do ketone reduction to alcohol with NaBH4. After this the alcohol obtained is to be reacted with ethyl bromide and NaH. Is it necessary to remove excess NaBH4 and neutralize before going to etherification step? Also which solvent may be the best for the first reduction step?
Dear Sudheesh N,
I think that your reaction will undergo two steps
1) the Ketone reduction
2) the williamson ether synthesis
In the fist step, after stirred magnetically the reactional medium with an excess of NaBH4, the reaction is stopped by adding the equivalent of H2O in the medium ( 0.314mmol of Ketone for 50ml of H20); The organic layer is then extract with DCM and dry with Na2SO4 anhydrous;
You eventually continuous the second step, which is the estertifcation.
Good luck
Dr Ernestine Nkwengoua Zondegoumba, S. Lecturer, UYI, Yaounde-Cameroon.
Dear Sudheesh N,
The medium for your first step should be a solvent, which dissolves your ketone. You should follow the progress of the reduction by TLC and quench the excess of sodium borhydride with water or alcohol. Remove the solvents and dry the product. Add dry solvent (dry tetrahydrofuran works very well), add NaH and when the bubbling (hydrogen evolution) stops add your bromide. The reaction should be performed under dry inert gas (nitrogen or argon). Sometimes it is better to mix the two reagents (alcohol and bromide) dissolve them in the selected solvent and then add the NaH. This sequence works well when there are no other potentially interfering functional groups. Good luck!
Ivan Gitsov
Reduction step: keto compound+ NaBH4 stirred at 0 oC then RT (monitored the reaction bt TLC) after completion add acetone or NH4Cl to remove excess sodium borohydide then concentrate the reaction mixture under reduced pressure. The reaction mixture was diluted with water and extracted with DCM solvent for 2 times. The organic layer concentrated under reduced pressure. and used for the next transformation.
Etherification reaction: To the stirred solution of NaH in THF/DMF at 0 oC was added alcohol over 10 min. The RM was stirred for 10 min followed by addition of bromo comp. over 5 min. the reaction was monitored by TLC if starting material as it is then add TBAHSO4 (phase transfer cat.)
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