Study on the Mechanism of a Novel Tandem Reaction to Produce Substituted lmidazo[1,5-a]pyridine Derivatives

【摘要】：正The mechanism of a novel tandem reaction (Eq. 1) to produce substituted imidazo[1,5-a]pyridine derivatives has been investigated using RHF and B3LPY theories. Solvent effects were studied with the Onsarger model and the CPCM model using the dielectric constant (37.0) of DMF. The results reveal that the whole reaction is composed of four steps: deprotonation, novel Claisen cyclization, 1,3-proton shift and dehydroxylation, and the 1,3-proton shift is the rate-determining step (Figures 1 and 2). Basic condition is favorable. Solvent effects have a marked consequence on the reaction, especially on deprotonation. In the gas phase, deprotonation is very fast, whereas in the polar solvent it is difficult and becomes the rate-determining step. Furthermore, solvent effects decrease the relative free energy of product dramatically.