Organocatalytic Nazarov-type cyclization of 3-alkynyl-2-indolylmethanols: construction of axially chiral cyclopenta[b]indole scaffolds

In recent years, it has become an urgent task to design new types of indole-based platform molecules for Nazarov-type cyclizations and develop organocatalytic synthesizing indole derivatives. To fulfill this task, in work, by changing the alkynyl terminal substituent from t-Bu aryl group, reactivity 3-alkynyl-2-indolylmethanols is modulated serve as competent substrates Brønsted acid-catalyzed cyclization. Based on reactivity, first cyclization aryl-substituted with 2-naphthols accomplished, leading efficient construction a class axially chiral 3, 4-dihydrocyclopenta[b]indole scaffolds. This preliminary investigation asymmetric provides optional strategy atroposelective cyclopenta[b]indole addition, preparation optical purity established through resolution, which could complementary method catalytic approaches.