From CO2 to 4 H-Quinolizin-4-ones: A One-Pot Multicomponent Approach via Ag2O/Cs2CO3 Orthogonal Tandem Catalysis.

Using carbon dioxide as a C1 precursor, here we report relatively simple and cost-effective orthogonal tandem catalysis, namely Ag2O in conjunction with Cs2CO3 serves to promote a multicomponent tandem reaction forming two new C-C and one new C-N bonds. 4 H-Quinolizin-4-ones, key skeletal components in a variety of biologically active molecules, were obtained with yields up to 99%. The present approach features a broad substrate scope and mild reaction conditions and benefits from using cost-effective reaction and catalysts.