Organocatalytic Fischer Indolization Using the 2,2′-Biphenol/ B(OH)3 System

AbstractAn organocatalyzed Fischer indolization is established by combining 2,2′-biphenol (10 mol%) and B(OH)3 (30 mol%) as weak, readily available, and easy-to-handle acids. The inclusion of MgSO4, which efficiently scavenges NH3 (a possible acid catalyst poison), appears to be key to the success of this process. The corresponding indoles are obtained in yields of up to 91% using this method.y