Reductive CO2 Fixation via the Selective Formation of C-C Bonds: Bridging Enaminones and Synthesis of 1,4-Dihydropyridines.

Herein, a selective tandem C-C bond-forming reaction with CO2 was developed to realize the bridging of enaminones and synthesis of 1,4-dihydropyridines, respectively. n-Butylamine significantly promoted this CO2 deoxymethylenation procedure catalyzed by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and ZnCl2. The mechanism involving the formation of bis(silyl)acetal, nucleophilic addition, and amine elimination was also interpreted to clarify the bridging of two molecules of enaminones with CO2 and the generation of dihydropyridine derivatives.