An efficient and expedient approach for the synthesis of unsymmetrical 3,3′-Bis-indolylmethanes via silica gel-mediated Friedel-Craftsalkylation of 3-indolylmethanols with diverse indoles is described. The synthetic utility of this transformation was demonstrated by reusing silica gel up to 10 times without apparent loss of reactivity .
Construction of Novel Tetrahydro-<i>β</i>-carboline-1-thione Spirooxindoles by Brønsted Acid Mediated Formal [3+3] Cyclization of 3-Indolylmethanols with 3-Isothiocyanato Oxindoles
p‐Toluenesulfonic acid mediated formal [3+3] cyclization of 3‐indolylmethanols with 3‐isothiocyanato oxindoles was realized. This transformation allowed for the synthesis of a series of novel tetrahydro‐β‐carboline‐1‐thione spirooxindoles in moderate to excellent yields (up to 99%) with generally good diastereoselectivities (up to >20:1). The structure of one product was determined by an X‐ray crystal
The first enantioselective synthesis of pyrrolyl-substituted triarylmethanes has been accomplished using a novel imidodiphosphoric acid catalyst, which is derived from two (R)BINOL frameworks with different 3,3'-substituents. This strategy was also expanded to the synthesis of bis(indolyl)-substituted triarylmethanes with high enantioselectivities, which could only be obtained with moderate ee values in previous reports. These two efficient Friedel-Crafts alkylation processes feature low catalyst loading, broad functional group compatibilities, and the potential to provide practical pathways for the synthesis of enantioenriched bioactive triarylmethanes.