Ammonium tetrafluoroborate: Novel Unprecedented Catalyst for the Synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones through Biginelli Reaction

Abstract A novel method has been developed to use ammonium tetrafluoroborate (NH 4 BF 4 ) directly as catalyst in Biginelli reaction. A new paradigm of the Biginelli reaction for the synthesis of 3,4‐dihydropyrimidin‐2(1 H )‐ones derivatives found the use of ammonium tetrafluoroborate as a novel, inexpensive, readily available, non‐toxic and mild catalyst in good to excellent yields. Notably, this is the first time that ammonium tetrafluoroborate is directly used as a catalyst in organic synthesis. So far, no organic reaction is available in literature where NH 4 BF 4 is directly used as catalyst. However, some reactions are found where NH 4 BF 4 is used with other catalysts as promoters or additives. The protocol developed has several advantages, such as highly efficient, simple, atom‐economical, environmentally friendly, easy synthetic and purification methods.