An Iridium(I) N‐Heterocyclic Carbene Complex Catalyzes Asymmetric Intramolecular Allylic Amination Reactions

Abstract

A chiral iridium(I) N-heterocyclic carbene complex was reported for the first time as the catalyst in the highly enantioselective intramolecular allylic amination reaction. The current method provides facile access to biologically important enantioenriched indolopiperazinones and piperazinones in good yields (74-91 %) and excellent enantioselectivities (92-99 % ee). Preliminary mechanistic investigations reveal that the C-H activation occurs at the position ortho to the N-aryl group of the ligand.

Diastereodivergent synthesis of enantioenriched α,β-disubstituted γ-butyrolactones via cooperative N-heterocyclic carbene and Ir catalysis

“…Interestingly, no reaction occurred when Ir(4a)(COD)Cl (complex 13) was used in catalytic amounts, in the presence of 8 mol% L4 and under otherwise identical reaction conditions (entry 7). [46][47][48] Based on these preliminary mechanistic investigations, we propose the reaction to begin with the formation of (Z)-enol intermediate B from ,-unsaturated aldehyde via homoenolate formation followed by facile -protonation 49 (or from -chloroaldehydes via base-mediated elimination of chloride 42 ) (Fig. 7b).…”

Enantioselective Catalytic Synthesis of N-alkylated Indoles

“…These results were comparable to the results obtained with an in situ formed catalyst (82% yield, 99% ee). An efficient route for the synthesis of chiral indolopiperazinones was proposed by You and coworkers (Scheme 25) [53]. The intramolecular allylic amination of indole derivatives 121 was catalyzed by an iridium(I) NHC complex generated from the salt 123 and [Ir(cod)Cl] 2 in the presence of DBU in dichloromethane at room temperature.…”

An Iridium(I) N‐Heterocyclic Carbene Complex Catalyzes Asymmetric Intramolecular Allylic Amination Reactions

“…Thes tructure of C1 was confirmed by X-ray diffraction analysis (see the Supporting Information). [25] Ap reliminary mechanistic study was carried out to shed light on the active catalytic species.T op robe the possible existence of the C À Hactivation of the catalyst, we treated C1 with AgBF 4 in [D 6 ]benzene.Asinglet at d = À35.6 ppm was observed by 1 HNMR spectroscopy after 10 minutes and it was assigned as ahydride [Eq. (2)].…”