Abstract
An efficient room-temperature procedure was developed for Knoevenagel condensation of various aldehydes with malononitrile and ethyl cyanoacetate in the presence of triethylamine and catalytic amounts of magnesium bromide diethyl etherate.
Highlights
The synthesis of electrophilic olefins from active methylene and carbonyl compounds, known as the Knoevenagel condensation,1 is one of the most well known reactions in organic chemistry owing to its applicability in the preparation of various synthetic targets
We first examined the reaction between aromatic aldehydes and malononitrile in THF by using different quantities of MgBr2.OEt2 and equimolar amount of TEA
When a mixture of benzaldehyde and malononitrile was treated under the conditions cited, TLC showed complete disappearance of the starting aldehyde in less than 1h and the 1HNMR spectrum showed the presence of the compound 3a as the sole product in the reaction mixture
Summary
The synthesis of electrophilic olefins from active methylene and carbonyl compounds, known as the Knoevenagel condensation,1 is one of the most well known reactions in organic chemistry owing to its applicability in the preparation of various synthetic targets.2 Many modifications have been made to this process in recent years using Lewis acid catalysis,3 ionic liquids,4 microwave irradiation,5 quaternary ammonium salts,6 heterogeneous catalysts,7 and organo-base mediation.8 in many of these methods relatively harsh conditions are required, expensive reagents are involved, or a combination of several additives is employed. Knoevenagel condensation of various aldehydes with active methylene compounds in the presence of triethylamine (TEA) (Scheme 1). We first examined the reaction between aromatic aldehydes and malononitrile in THF by using different quantities of MgBr2.OEt2 and equimolar amount of TEA.
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