Synthesis and Characterization of Donor–Acceptor Iron Porphyrin Carbenes and Their Reactivities in N–H Insertion and Related Three-Component Reaction

Abstract

Iron porphyrin carbenes (IPCs) have been extensively recognized as the reactive intermediates in various iron porphyrin-catalyzed carbene transfer reactions. While donor–acceptor diazo compounds have been frequently used for such transformations, the structures and reactivities of donor–acceptor IPCs are less explored. To date, no crystal structures of donor–acceptor IPC complexes have been reported, and therefore, the involvement of IPC intermediacy for such transformations lacks direct evidence. Here we report the synthesis and NMR characterization of several donor–acceptor IPC complexes from iron porphyrin and corresponding donor–acceptor diazo compounds. The X-ray crystal structure of an IPC complex derived from a morpholine-substituted diazo amide was obtained. The carbene transfer reactivities of those IPCs were tested by the N–H insertion reactions with aniline or morpholine as well as the three-component reaction with aniline and γ,δ-unsaturated α-keto ester based on electrophilic trapping of an ammonium ylide intermediate. Based on these results, IPCs were identified as the real intermediates for iron porphyrin-catalyzed carbene transfer reactions from donor–acceptor diazo compounds.

Recent Synthetic Advances on the Use of Diazo Compounds Catalyzed by Metalloporphyrins

“… Synthesis of iron porphyrin carbene complexes and the corresponding catalyzed N−H insertion reactions with aniline or morpholine [ 42 ]. …”

“…However, the m pholine-derived amide complex could only react with aniline to deliver the correspondi N−H insertion product with very poor efficiency. Hence, iron porphyrin carbenes w identified as the real intermediates for iron porphyrin-catalyzed carbene transfer reactio from donor-acceptor diazo compounds [42]. Fe(TPP)Cl also catalyzes the insertion of benzylic carbenes, generated in situ from Ntosylhydrazones derived from different benzaldehydes, into X−H (X = Si, Sn, Ge).…”

“…However, the morpholinederived amide complex could only react with aniline to deliver the corresponding N−H insertion product with very poor efficiency. Hence, iron porphyrin carbenes were identified as the real intermediates for iron porphyrin-catalyzed carbene transfer reactions from donor-acceptor diazo compounds [42]. Scheme 6.…”

Old Magician, New Magic: Dirhodium Tetracarboxylates, Unprecedented Bifunctionality in Metallaphotocatalysis

“…Glorious (7), Gevorgyan (8), Shang and Fu (9), Bach (10), Meggers (11), Xiao (12), Chen (13) and others (14,15) have developed photosensitizer-tethered bifunctional catalysts which were generated from elegant design and remarkable synthesis. Our group has a lasting interest in transitional metal-catalyzed carbene-based reactions (16)(17)(18)(19). Here, we intend to nd a bifunctional transitional metal catalyst to connect carbene chemistry with photochemistry.…”

Heterogeneous Iridium-Catalyzed Carbene N–H Bond Insertion with α-Alkyl Diazo Esters

“…Transition-metal-catalyzed carbene insertion into N–H bonds has emerged as a robust method for constructing C–N bonds, enabling the synthesis of diverse nitrogen-containing bioactive compounds and pharmaceuticals. − While numerous successful examples exist, the exploration of α-alkyl diazo esters as carbene precursors remains limited (Scheme ). The competitive β-hydride elimination pathway often hinders the desired reactions under homogeneous conditions, resulting in low yields of the desired products. − Inspiringly, the Zhou group reported on the strategy using achiral metal complexes combined with chiral phosphoric acids for asymmetric carbene N–H insertion. , while the Feng group achieved catalytic asymmetric homologation of ketones using α-alkyl diazo esters, with chiral scandium­(III) N,N ′-dioxide as a Lewis acid catalyst. − These significant research results encouraged us to explore the carbene insertion reaction with this type of a challenged substrate via heterogeneous catalysis.…”