[kamiyu]

I have read a precedure involving NaH that functions to deprotonates alcohol.

But the procedure mentioned degassing of solvent (DMSO), I wonder if the NaH will be quenched by oxygen?

[Eloquentia]

Could be that in their case the starting material is oxygen sensitive? I work with sodium hydride usually in commercially available dry DMF and never had to degas it. I avoid DMSO because it is very hard to keep it dry and to get rid of it after the reaction. In case of DMF, ether or ethyl acetate is added after the reaction is complete and the organic phase is washed with 5% aq Lithium chloride. Lithium ions form a highly water soluble complex with DMF and it goes into the aqueous phase.

[Archer]

I usually use NaH in THF for deprotonation reactions, although in my experience the process is sluggish.

I use DMSO only if I need to solubilise everything. Never degassed it prior to use though.

Could be that in their case the starting material is oxygen sensitive? I work with sodium hydride usually in commercially available dry DMF and never had to degas it. I avoid DMSO because it is very hard to keep it dry and to get rid of it after the reaction. In case of DMF, ether or ethyl acetate is added after the reaction is complete and the organic phase is washed with 5% aq Lithium chloride. Lithium ions form a highly water soluble complex with DMF and it goes into the aqueous phase.

This sounds good, not a fan of DMF for safety reasons but this may work better for my reaction.

[kamiyu]

Thanks for all your replies.

Luckily my reaction has been tackled and I manage to get sth 70-80% yield with very clean crude product mixture. Just would like to add some points:

1) NaH, if handled in air (not glove box), is always contaminated by NaOH. The NaOH may or may not affect your reaction, depending on what you are doing. But for THF, NaOH will not dissolve in THF even when it is heated and thus there is no need to concern about the SN2 reaction towards, say, CH2Br (my substrate) by NaOH.

2) NaH does not react with Si-Cl, CH3-I, and benzyl bromide. The reason is the small s-orbital of hydride is not large enough to fit with the anti bonding orbital.

3) I use excess NaH to accomplish the reaction and it went very nice.

[Eloquentia]

This sounds good, not a fan of DMF for safety reasons but this may work better for my reaction.

Good point! One of course should use an ice bath to cool the reaction and add sodium hydride portionwise. Under these conditions and on a lab scale it is possible to control the temperature.

[discodermolide]

It's better and safer to suspend the NaH in the solvent and add the substrate drop wise.
Adding reactive solids portion-wise can be a hazard.