Reaction #64684

Reaction equation

veratraldehyde

diethyl 3,4-di-(methoxy)-benzylmalonate

Meldrum's acid

→

3,4-dimethoxyhydrocinnamic acid

ethyl 3,4-di-(methoxy)-hydrocinnamate

Solvents

formic acid

triethylamine

ethanol

formic acid

triethylamine

Conditions

Workup

1. 1
   Otherat 100° C.
2. 2
   Otherfor 2 hours

Procedure

By boiling Meldrum's acid (formula III with R9 =R10 =methyl group) with veratraldehyde in an ethanolic medium in the presence of formic acid and triethylamine, monoethyl 3,4-di-(methoxy)-benzylmalonate was obtained. According to our experimental observation, diethyl 3,4-di-(methoxy)-benzylidene malonate could not be hydrogenated to diethyl 3,4-di-(methoxy)-benzylmalonate when using formic acid and triethylamine as reagents. Furtheron we have observed that by reacting veratraldehyde with Meldrum's acid, formic acid and triethylamine at 100° C. for 2 hours and then by boiling with ethanol for 2 hours 3,4-dimethoxyhydrocinnamic acid and not ethyl 3,4-di-(methoxy)-hydrocinnamate was obtained as final product. Thus, the reaction can be interpreted only in such a way that 5-[3',4'-di-(methoxy)-phenylmethyl]-Meldrum's acid is formed in the manner described above, the dioxane ring of which is opened and one carboxyl group of the 3,4-di-(methoxy)-benzylmalonic acid formed is simultaneously esterified. When the temperature of the reaction mixture is increased after removing the ethanol, the carboxyl group is eliminated and 3,4-di-(methoxy)-hydrocinnamic acid ester is obtained.

Source