Is this one of your starting compound?

Is this your reaction?

When this is the reaction which Carlos showed us you should use another base. Li+ is small and able to form a stable chelate with your starting material. KOtBu in dry THF or 1,4-dioxane may be work. Do not use methanolate or ethanolate! This can cause transesterification. When you have a microwave oven use it. These kind of reaction will work very well in there.

Under those reaction conditions, 3-bromopropionate will eliminate to give the corresponding ethyl acrylate. This is where your 1 eq. of base is going. So either you use ethyl acrylate directly as your electrophile or you add more base. If transesterification is not an issue for you, I would run it as follow:

2.2 eq. of sodium in ethanol, stir under cooling and under nitrogen until there's no more solid. Add. both reagents and warm to reflux overnight.

Good luck!

Also, in reference to Mr. Heller's comment, Lithium will indeed form a 6-membered chelate, but the enol will still react readilly. Chelate control is a common way of controling stereoselectivity in aldol reactions, so I don't think it is an issue in your case.

Thank you very much to all of you..what a great explaination there..i will try again at the lab..Can't wait.. Thanks again. Wish me luck..

I have one more question to ask, if i want to react ethyl-3-bromopropinoate with this compound, 1-methyl-3,3-dimethylprrolidin-2,4-dione, what is the base i can use?does it required strong base to deprotonate at carbon 5?

I think LiHMDS will be strong enough.

LiHMDS, could be quite effective for your work. The LiHMDS with TMCDA/TMEDA/DME/THF would be the option to try.

LiHMDS forms the ligands with them and are useful in enolization.

Check out the paper attached by Peter F. Godenschwager and David B. Collum*, which will clear your doubts.

Thanks Mr. Prashant Kapse