[masaa]

Hi Guys

I have a reaction an addition reaction between an alkyne (Dimethyl acetylenedicarboxylate) with an aromatic  (4-nitrobenzaldehyde ) in the presence of pyridine.

 The reaction should be placed in ice path and cooled to -20 C for 15 min , then will be placed in room temperature .  I am thinking of using ice and salt to maintain this temperature or dry ice with methanol.

The problem is that I do not understand why we need to cool the reaction down to - 20C , is it because the initiation start at that temperature or the  reaction associated with temperature release.
Many Thanks

[pgk]

As far as I know, the reaction of dimethyl acetylenedicarboxylate and an aromatic aldehyde alone, does not give any product. However, the mixture of dimethyl acetylenedicarboxylate and an aromatic aldehyde often figures in three component reactions together with a strong nucleophile (e.g. a phenol). Thus, the low initial temperature might be related with the stability of the third component (nucleophile), as well as with the base strength.
On the other hand, the low initial temperature might also mean a highly exothermic reaction or kinetic vs. thermodynamic control. How is the addition of the reagents in the prototype reference, slow (exothermic reaction) or fast (kinetic control)?

[orgopete]

Hint, Baylis-Hillman?

[pgk]

Acrylate esters rather than propiolate ones, figure in the ordinary Baylis-Hillman reaction. However, propiolate esters can also participate in the three component version of the Baylis-Hillman reaction.