Nucleophilic tertiary amine, catalytic role

The Baylis-Hillmann reaction is another bench-mark reaction in which ionic liquids have been successfully tested. The catalytic cycle of the Baylis-Hillmann reaction is reported in Figure 7. The catalyst is a highly nucleophilic tertiary amine, generally DABCO, or a tertiary phosphine, which adds to the oc,p-unsaturated electrophile in a 1,4 fashion to deliver an enolate which, in turn, adds to the aldehyde. The critical step is now a proton transfer from the enolisable position to the oxygen atom this process is catalysed by an alcohol which plays the role of a proton shuttle between the two foregoing positions. Once a P-ammonium enolate is formed, a rapid P-elimination takes place, delivering the Baylis-Hillmann condensation product. 

The pioneering studies in this field are done by Pracejus and coworkers in a series of papers published in the 1960s in which they studied the asymmetric addition/protonation of alcohols to ketenes [8]. They carried out a number of experiments to demonstrate the catalytic role of a tertiary amine on the nucleophilic... 

Addition of a basic catalysts (W,N -dimethylbenzylamine) results in a considerable increase in the reaction rate of phenol with both cycloaliphatic and glycidyl epoxy groups. The rise of reactivity of 3-cyclohexene-l-methyl glycidyl ether XVIII is especially strongly pronounced. The catalytic role of the tertiary amine consists in an increase in the nucleophilic activity of phenol as the proton donor as a result of proton withdrawal. 

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