Study of Michael-Michael-retro Michael addition catalyzed by 9-amino-9-deoxyepiquinine using ESI-MS.

The Michael-Michael-retro Michael addition catalyzed by 9-amino-9-deoxyepiquinine was monitored and the major intermediates and catalyst in the catalytic cycle were detected and characterized using ESI-MS/MS for the first time. Some important isomeric intermediates including isomeric enamine and imine structures were tentatively differentiated and further studied by theoretical calculations. Fragment ions of protonated catalyst indicate that proton possibly influences the conformation of the catalyst.