Acid-free and base-free [2+2+2] cyclization of vinyl thianthrenium salts and nitriles for the construction of pyrimidine derivatives

Pyrimidine derivatives are crucial in pharmaceuticals and materials science. We present a sustainable, metal- and additive-free method to synthesize 2,4,6-trisubstituted pyrimidines under mild conditions. Vinyl thianthrenium salts, generated from alkynes, undergo cyclization with aryl- or alkyl-nitriles to afford pyrimidine derivatives in yields of up to 87%. The protocol demonstrates broad substrate tolerance, accommodating both electron-donating and electron-withdrawing groups. Its simplicity, scalability, and environmentally benign nature highlight its value in heterocycle synthesis.