C–H Insertion Catalyzed by Tetratolylporphyrinato Methyliridium via a Metal–Carbene Intermediate

Anding, Bernie J.; Brgoch, Jakoah; Miller, Gordon J.; Woo, L. Keith

doi:10.1021/om3005433

Cited by 30 publications

(43 citation statements)

References 43 publications

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“…Detection of the Ir-QC intermediate was subsequently carried out. Addition of N 2 QC tBu into aC DCl 3 solution of [Ir(TTP)Me] at À50 8 8Cled to the formation of anew species with ad ownfield shift for Ir-CH 3 at d = À4.51 ppm (Scheme 4a;s ee Figure S1), which is comparable to that observed for [Ir(TTP)(Me)(C(Ph)CO 2 Me)] (d = À4.80 ppm) [14] and is tentatively assigned to [Ir(TTP)(Me)(QC tBu )].H owever,i t could only be formed in about 10 %y ield, and further addition of diazo precursor caused its decomposition to the azine product (Scheme 4a). [15] This intermediate was also detected by MALDI-HRMS (matrix-assisted laser desorption/ionization-high resolution mass spectrometry) in which both the experimental m/z values and isotopic pattern are consistent with its formulation (Scheme 4b).…”

Section: Angewandte Chemiesupporting

confidence: 54%

Iridium(III)‐Catalyzed Intermolecular C(sp³)−H Insertion Reaction of Quinoid Carbene: A Radical Mechanism

et al. 2019

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Described herein is an Ir III /porphyrin-catalyzed intermolecular C(sp 3 ) À Hi nsertion reaction of aq uinoid carbene (QC). The reaction was designed by harnessing the hydrogen-atom transfer (HAT) reactivity of am etal-QC species with aliphatic substrates followed by aradical rebound process to affordC À Harylation products.This methodology is efficient for the arylation of activated hydrocarbons such as 1,4-cyclohexadienes (down to 40 min reaction time,upto99% yield, up to 1.0 gs cale). It features unique regioselectivity, which is mainly governed by steric effects,asthe insertion into primary CÀHbonds is favored over secondary and/or tertiary CÀHb onds in the substituted cyclohexene substrates.M echanistic studies revealed ar adical mechanism for the reaction.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

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Section: Angewandte Chemiesupporting

confidence: 54%

Iridium(III)‐Catalyzed Intermolecular C(sp³)−H Insertion Reaction of Quinoid Carbene: A Radical Mechanism

et al. 2019

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“…This is noteworthy, given the propensity of EDA to dimerize during cyclopropanation and C−H insertion reactions, which are typically carried out using excess substrate. 29,32 In addition, some of the reactions for double insertion exhibited a fleeting color change, signifying the presence of an observable intermediate.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Iridium Porphyrin Catalyzed N–H Insertion Reactions: Scope and Mechanism

Anding

Woo

2013

Organometallics

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Ir(TTP)CH3 catalyzed N-H insertion reactions between ethyl diazoacetate (EDA) or methyl phenyldiazoacetate (MPDA) and a variety of aryl, aliphatic, primary, and secondary amines to generate substituted glycine esters with modest to high yields. Aniline substrates generally gave yields above 80%, with up to 105 catalyst turnovers, and without slow addition of the diazo reagent. Good yields were also achieved with aliphatic amines, though higher catalyst loadings and slow addition of the amine were necessary in some cases. Primary amines reacted with EDA to generate both single-and double-insertion products, either of which could be produced selectively in high yield with the proper choice of stoichiometric ratios and reaction temperature. Notably, mixed trisubstituted amines, RN(CH2CO2Et)(CHPhCO2Me), were generated from the insertion of 1 equiv of EDA and 1 equiv of MPDA into primary amines. The N-H insertion mechanism was examined using substrate competition studies, trapping experiments, and multiple spectroscopic techniques. Substrate competition studies using pairs of amines with EDA or MPDA revealed Hammett correlations with respective slopes of ρ = 0.15 and ρ+ = −0.56 as well as kinetic isotope ratios of kH/kD = 1.0 ± 0.2 and 2.7 ± 0.2. Competitive amine binding to the iridium center was demonstrated by kinetics and equilibrium binding studies. Equilibrium binding constants ranged from 102 to 105. Monitoring the reaction by absorption spectroscopy revealed a transient metalloporphyrin complex. The lifetime of this species was dependent on the nature of the amine substrate, which suggests that the catalytic cycle proceeds through a metal-ylide intermediate.

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“…In contrast, the trans-methyl signal of Ir(TTP)CH 3 (C(Ph)-CO 2 Me) shifted downfield to −4.8 ppm. 15 Variable-Temperature NMR Analysis. At ambient temperature, complexes 5a,b and 6a,b displayed several broad NMR resonances.…”

Section: Synthesis and Characterization Of Diaminocarbenementioning

confidence: 99%

“…For example, DFT optimization of a species that is active for carbene transfer, Ir(TTP)CH 3 (C(Ph)CO 2 CH 3 ), revealed notable porphyrin distortion in the ruffling (−0.4513) and doming (−0.2309) modes, with an overall D oop of 0.5154. 15 Medforth et al previously proposed a deformability model, which suggests that the barrier for meso-aryl−porphyrin C−C bond rotation lowers upon increased ruffling of the metalloporphyrin. 31 Rotation barriers and NSD data for NHC complexes 5b and 6b are consistent with this model.…”

Section: Synthesis and Characterization Of Diaminocarbenementioning

confidence: 99%

Comparative Study of Rhodium and Iridium Porphyrin Diaminocarbene and N-Heterocyclic Carbene Complexes

2014

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Iridium meso-tetratolylporphyrinato (TTP) mono-and bis-diaminocarbene complexes, [Ir(TTP)[═C(NHBn)(NHR)]2-x(C≡NBn)x]BF4, where R = Bn, n-Bu and x = 1, 0, were synthesized by nucleophilic addition of amines to the bis-isocyanide complex [Ir(TTP)(C≡NBn)2]BF4. Rhodium and iridium porphyrinato N-heterocyclic carbene (NHC) complexes M(TTP)CH3(NHC), where NHC = 1,3-diethylimidazolylidene (deim) or 1-(n-butyl)-3-methylimidazolylidene (bmim), were prepared by the addition of the free NHC to M(TTP)CH3. The NHC complexes displayed two dynamic processes by variable-temperature NMR: meso-aryl-porphyrin CC bond rotation and NHC exchange. meso-Aryl-porphyrin CC bond rotation was exhibited by both rhodium and iridium complexes at temperatures ranging between 239 and 325 K. Coalescence data for four different complexes revealed ΔG⧧ROT values of 59 ± 2 to 63 ± 1 kJ•mol-1. These relatively low rotation barriers may result from ruffling distortions in the porphyrin core, which were observed in the molecular structures of the rhodium and iridium bmim complexes. Examination of NHC exchange with rhodium complexes by NMR line-shape analyses revealed rate constants of 3.72 ± 0.04 to 32 ± 6 s-1 for deim displacement by bmim (forward reaction) and 2.7 ± 0.4 to 18 ± 2 s-1 for bmim displacement by deim (reverse reaction) at temperatures between 282 and 295 K, corresponding to ΔGf⧧ of 65.2 ± 0.6 kJ•mol-1 and ΔGr⧧ of 66.2 ± 0.5 kJ•mol-1, respectively. Rates of NHC exchange with iridium were far slower, with first-order dissociation rate constants of (1.75 ± 0.04) × 10-4 s-1 for the forward reaction and (1.2 ± 0.1) × 10-4 s-1 for the reverse reaction at 297.1 K. These rate constants correspond to ΔG⧧ values of 94.2 ± 0.6 and 95.2 ± 0.2 kJ•mol-1 for the forward and reverse reactions, respectively. Equilibrium constants for the exchange reactions were 1.6 ± 0.2 with rhodium and 1.56 ± 0.04 with iridium, favoring the bmim complex in both cases, and the log(K) values for NHC binding to M(TTP)CH3 were 4.5 ± 0.3 (M = Rh) and 5.4 ± 0.5 (M = Ir), as determined by spectrophotometric titrations at 23 °C. The molecular structures also featured unusually long metal-Ccarbene bonds for the bmim complexes (Rh-CNHC: 2.255(3) Å and Ir-CNHC: 2.194(4) Å).

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C–H Insertion Catalyzed by Tetratolylporphyrinato Methyliridium via a Metal–Carbene Intermediate

Cited by 30 publications

References 43 publications

Iridium(III)‐Catalyzed Intermolecular C(sp³)−H Insertion Reaction of Quinoid Carbene: A Radical Mechanism

Iridium(III)‐Catalyzed Intermolecular C(sp³)−H Insertion Reaction of Quinoid Carbene: A Radical Mechanism

Iridium Porphyrin Catalyzed N–H Insertion Reactions: Scope and Mechanism

Comparative Study of Rhodium and Iridium Porphyrin Diaminocarbene and N-Heterocyclic Carbene Complexes

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C–H Insertion Catalyzed by Tetratolylporphyrinato Methyliridium via a Metal–Carbene Intermediate

Cited by 30 publications

References 43 publications

Iridium(III)‐Catalyzed Intermolecular C(sp3)−H Insertion Reaction of Quinoid Carbene: A Radical Mechanism

Iridium(III)‐Catalyzed Intermolecular C(sp3)−H Insertion Reaction of Quinoid Carbene: A Radical Mechanism

Iridium Porphyrin Catalyzed N–H Insertion Reactions: Scope and Mechanism

Comparative Study of Rhodium and Iridium Porphyrin Diaminocarbene and N-Heterocyclic Carbene Complexes

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Iridium(III)‐Catalyzed Intermolecular C(sp³)−H Insertion Reaction of Quinoid Carbene: A Radical Mechanism

Iridium(III)‐Catalyzed Intermolecular C(sp³)−H Insertion Reaction of Quinoid Carbene: A Radical Mechanism