Finding the Best Proposed Mechanism for Ugi Multi-Component Reaction by DFT Study

The one-pot four-component condensation of benzoic acid (R1), aniline (R2), benzaldehyde (R3), and 2-isocyano-2-methylpropane was investigated at the B3LYP/6-311G** level to explore the reaction mechanism as a theoretical study. All routes were studied and structure of intermediates (IM) was optimized and all of the respective transition states (TS) were found. The calculation results proved that the proposed mechanism consists of eight steps that rate determining the state is nucleophilic attack of isocyanide to benzaldehyde.