Multi-component Reactions General Concept and Examples

4 Multi-component Reactions General Concept and Examples 

The organocatalytic Petasis reaction is a three-component reaction, since in the critical step of the reaction process one molecule of thiourea catalyst, an A -acylquinolinium or A -acyliminium ion, and boronic acid form the productive complex. It represents a specific case of an MCR in the sense that one component has a catalytic effect in promoting covalent bond formation between the other two partners. It is important to emphasize, however, that in MCRs not all reacting molecules undergo simultaneous interaction, which represents an entropically highly unfavourable event. Rather, an MCR is a well-defined sequence of bimolec-ular interactions, in which the intermediate formed during the first and the second stages, interacts with the third, and in some cases with the fourth component in the MCR. 

---