Strong and Confined Acids Catalyze Asymmetric Intramolecular Hydroarylations of Unactivated Olefins with Indoles

Abstract

In recent years, several organocatalytic asymmetric hydroarylations of activated, electron-poor olefins with activated, electron-rich arenes have been described. In contrast, only a few approaches that can handle unactivated, electronically neutral olefins have been reported and invariably require transition metal catalysts. Here we show how an efficient and highly enantioselective catalytic asymmetric intramolecular hydroarylation of aliphatic and aromatic olefins with indoles can be realized using strong and confined IDPi Brønsted acid catalysts. This unprecedented transformation is enabled by tertiary carbocation formation and establishes quaternary stereogenic centers in excellent enantioselectivity and with a broad substrate scope that includes an aliphatic iodide, an azide, and an alkyl boronate, which can be further elaborated into bioactive molecules.

Green Chemistry Meets Asymmetric Organocatalysis: A Critical Overview on Catalysts Synthesis

“… [177] No further insights will be given about these compounds, which have already been comprehensively reviewed, [179] due to their important achievements in organocatalysis. [ 180 , 181 ] For instance, IDPi were notably employed as Brønsted acidic catalysts to activate unbiased olefins by protonation [182] and even promoted Diels‐Alder reaction in parts per million loading. [183] Despite minimal possible modifications on the original protocol, the synthetic route is well‐established and relies on one‐pot phosphorylation of a proper 3,3′‐substituted derivative of 11 with a phosphorimidoyl trichloride, like compound 90 , and dimerization of the intermediate phosphorimidoyl chloride (which is not isolated) in the presence of HMDS.…”

Enantioselective Intermolecular Murai-Type Alkene Hydroarylation Reactions

“…[72][73][74] List and co-workers have disclosed intramolecular hydroheteroarylations of non-polarized alkenes with indole moieties (Scheme 4, C). 75 This method uses a chiral Brønsted acid catalyst (L2) to produce tertiary carbocations from alkenes in situ, and provides a broad range of tetrahydrocarbazoles possessing quaternary stereocenters.…”

(R)‐BINOL‐6,6’‐bistriflone: Shortened Synthesis, Characterization, and Enantioselective Catalytic Applications

“…Toward this end, the crucial influence of an electron‐withdrawing substituent, namely a NO 2 group, in the 6,6′‐positions of the BINOL scaffold was also demonstrated [11] . More generally, the introduction of a triflyl group proved determining for increasing catalytic activity [12–13] …”