[PRIYA1022]

I had been trying to do a condensation between cinnamaldehyde and nitromethane in methanol and NaOH  at 0^O C referring to  a literature procedure from a JACS paper.I follow the reaction via TLC and in about 45 min, I don't see any cinnamaldehyde..( I see a new spot..which I assume to be the product). However.I fail to get it during work up. I get back cinnamaldehyde and nitromethane.(as per the paper,the product is an unstable sodium salt that is filtered  and the obtained precipitate is dissolved quickly in crushed ice and hydrolyzed with cold HCl to obtain the desired nitrodiene as an yellow solid)
  I would appreciate any help/suggestions regarding this reaction.
Thank You.

[Custos]

Just guessing here. The first step in the Henry reaction is an aldol-like condensation to give an intermediate beta-hydroxy nitro compound right? Then you need to eliminate water to give your nitro alkene - and this should happen pretty readily. But perhaps you're seeing the aldol condensation product on TLC, then in workup rather than elimination of water you could be getting the reverse aldol back to starting materials. I'd try letting the reaction run longer -- perhaps allowing it to warm up to room temperature and stir overnight. Once the beta elimination of water occurs not much else can happen so there's not much harm in letting it run further.

[lavoisier]

If the method says that you need to isolate the 'sodium salt' first, then it means that the elimination occurs during the workup (most probably, when you add HCl). So, if the authors of the paper are right, you shouldn't expect your stuff to eliminate in basic conditions.

And in fact I remember that classic aldol reactions are more likely to proceed to elimination when they are done with acidic catalysis.

If you're strictly following the procedure, you should get the product. Are you doing exactly what they say, like keeping you stuff cold/warm, for the same time...?

The other possibility is to change the method, i.e. instead of using aq. NaOH, you can try ethanol/n-BuNH2, which is a standard protocol for Henry reaction. But if the authors used this method, there must be a reason, so I would advise you to stick with it and try to understand what you're doing wrong.

[PRIYA1022]

Hi,
  Thank you for the hint about elimination in acidic condition..( This concept just escaped my mind)
I did the reaction under different conditions and realized that elimination occurs at RT.It took 3 hours standing at RT after acidification and I saw the product separate as tiny yellow flakes.However my yield was less.I am at present working on obtaining a better yield.
Thanks once again.

[Kashinath.dhurke]

Please check the properties of B-hydroxy nitro compounds under basic conditions. you may find solution