Bi(OTf)₃-catalyzed addition of isocyanides to 2H-chromene acetals: An efficient pathway for accessing 2-carboxamide-2H-chromenes

Bismuth triflate (Bi(OTf)₃) is identified as an efficient catalyst for the direct addition of isocyanides to 2H-chromene acetals. The large scope of isocyanides and chromene acetals makes them suitable substrates in this catalytic system. By this synthetic strategy, a polyfunctional molecular scaffold, 2-carboxamide-2H-chromenes could be prepared efficiently in one step up to 95% yield. In addition, this efficient and practical protocol proceeded smoothly in the gram scale even when the catalytic loading was reduced to 2 mol%.