Baylis‐Hillman Reaction

AbstractThe Baylis‐Hillman reaction is a three‐component reaction involving the coupling of the α‐position of activated alkenes with carbon electrophiles (i.e., aldehydes) under the influence of a catalyst/catalyst system, with the characteristics of atom efficiency and the formation of dense functionality. Similarly, the corresponding reaction between alkenes and imines under same conditions is referred to as the aza‐Baylis‐Hillman reaction or aza‐Morita‐Baylis‐Hillman reaction. Some of the cases, this reaction is also cited as Morita reaction, Morita‐Baylis‐Hillman alkylation, and Morita‐Baylis‐Hillman cyclization. In this reaction, the activated alkenes include acrylonitrile, acrolein, acrylates, and α,β‐unsaturated ketones. Various types of the catalyst system have been applied in this reaction. Some shortcomings of the reaction have been reported, such as the slow reaction rate, being limited to electrophilic α,β‐unsaturated carbonyl compounds, and almost exclusively occuring in the reactions involving β‐unsubstituted α,β‐unsaturated carbonyl compounds and cyclic enones. Therefore, different measures have been taken to optimize this reaction.