Base‐Mediated Self‐Organization of Pyrimidines Versus Pyridines From Nitriles and Acetylene Gas: Solvent‐Controlled Selectivity

ABSTRACT The chemodivergent base‐mediated (KOH, 90°C, 10 min) reaction of aromatic (heteroaromatic) nitriles with acetylene gas to yield 2,4‐di(het)aryl pyrimidines (self‐organization of two molecules of nitrile and one molecule of acetylene) and 2‐(het)aryl pyridines (self‐organization of one molecule of nitrile and two molecules of acetylene) has been developed. The chemoselectivity of these cascade processes was found to be unusually strongly controlled by the composition of the solvent. The effect of sulfolane was especially pronounced: When added to DMSO, it enabled the synthesis of pyrimidines exclusively in yields of up to 71%, whereas in DMSO with a small amount of MeOH, only pyridines were formed in yields of up to 36%. Given the fact that acetylene gas is an industrially available feedstock, the synthesis of 2,4‐di(het)aryl pyrimidines developed here is becoming technologically feasible.