A New Homogeneous Catalyst for the Synthesis of 3,3′‐Bis(indolyl)methanes: Collective Synthesis of Arundine, Turbomycin B, Arsindoline A, and Tris(1H‐Indol‐3‐yl)methane*

An environmentally friendly, cost‐effective, and efficient method for synthesizing 3,3′‐bis(indolyl)methanes (BIMs) and their derivatives is developed through an electrophilic substitution reaction of indole with various aldehydes. This reaction is catalyzed by DABCO(TfOH) 2 , a homogeneous catalyst with 1,1,1,3,3,3‐hexafluoroisopropanol (HFIP) serving as a solvent. The process, performed exclusively in DABCO(TfOH) 2 , demonstrates excellent catalytic activity, yielding high product amounts (84%–98%) and showing broad functional group compatibility, which enables the efficient synthesis of both natural alkaloids and BIM derivatives. Interestingly, natural alkaloids are successfully synthesized to enhance the diversity of the compound library. Mechanistic studies highlight a delicate balance between fluorinated solvent, catalyst, and substrate as essential for achieving nature's approach to selective cyclization in organic synthesis.