Synergistic Photoredox Catalysis and Organocatalysis for Inverse Hydroboration of Imines

Abstract

The first catalytic inverse hydroboration of imines with N-heterocyclic carbene (NHC) boranes has been realized by means of cooperative organocatalysis and photocatalysis. This catalytic combination provides a promising platform for promoting NHC-boryl radical chemistry under sustainable and radical-initiator-free conditions. The highly important functional-group compatibility and possible application in late-stage hydroborations represent an important step forward to an enhanced α-amino organoboron library.

Direct Synthesis of N‐Heterocyclic Carbene‐Stabilized Copper Nanoparticles from an N‐Heterocyclic Carbene–Borane

“…Besides, NHC was essential to the stabilization of the NPs, as the reaction conducted with 2 equiv of TEMPO but without NHC–BH 3 produced few nanoparticles with ill‐defined shapes (Supporting Information, Figures S6 and S8C). Whereas NMR spectroscopy was neither sensitive nor discriminative enough, HRMS revealed new species: on using 4 equiv of TEMPO, the NHC–boryl radical/TEMPO adduct could be detected ([C 36 H 72 N 3 OB+H] + , calcd: 574.58412, found: 574.58384; Supporting Information, Figures S9–S12) . Therefore, the presence of a radical species (TEMPO) affected the ability of the NHC–borane to react with the copper precursor and to stabilize the nanoparticles.…”

“…Whereas NMR spectroscopy wasn either sensitive nor discriminative enough,H RMS revealed new species: on using 4equiv of TEMPO, the NHC-boryl radical/TEMPO adduct could be detected ([C 36 H 72 N 3 OB+ +H] + ,c alcd:5 74.58412, found: 574.58384;S upporting Information, Figures S9-S12). [35] Therefore, the presence of ar adical species( TEMPO) affected the ability of the NHC-borane to reactw ith the copper precursor and to stabilize the nanoparticles.…”

Light‐Driven Single‐Electron Transfer Processes as an Enabling Principle in Sulfur and Selenium Multicatalysis

“…In 2018, Zhu et al. successfully implemented the synergistic interplay of photoredox catalysis and sulfur‐catalyzed hydrogen atom transfer processes in the inverse hydroboration of imines (Scheme ) . Conceptually, the work was related to seminal investigations by Curran, Fensterbank, Malacria, and co‐workers on the chemistry of Lewis‐base‐stabilized boryl radicals derived from borane‐NHC adducts .…”

Lichtgetriebene Ein‐Elektronen‐Transferprozesse als Funktionsprinzip in der Schwefel‐ und Selen‐Multikatalyse

“…2018 konnten Zhu et al. die duale Photoredox/HAT‐Katalyse erfolgreich in der inversen Hydroborierung von Iminen implementierten (Schema ) . Konzeptionell ist diese Studie an Vorläuferarbeiten von Curran, Fensterbank und Malacria et al.…”