84250-69-1Relevant articles and documents
Access to Unsymmetrically Substituted Diaryl Gold N-Acyclic Carbene (NAC) and N-Heterocyclic Carbene (NHC) Complexes via the Isonitrile Route
Vethacke, Vanessa,Claus, Vanessa,Dietl, Martin C.,Ehjeij, Daniel,Meister, Arne,Huber, Jonas F.,Paschai Darian, Leon K.,Rudolph, Matthias,Rominger, Frank,Hashmi, A. Stephen K.
supporting information, p. 536 - 554 (2021/10/20)
A variety of unsymmetric diaryl gold N-acyclic carbene (NAC) complexes was synthesized via the isonitrile route by three different methods: (a) solvent free in a melt, (b) mechanochemically and (c) in THF at room temperature. The latter method can also be used to synthesize unsaturated gold NHC complexes. These methods overall offer access to a broad array of new complexes and remove one of the previous limitations of the isonitrile route to NAC and NHC complexes of gold, namely the inability to react with the less nucleophilic aromatic amines. The new complexes also proved to be successful as pre-catalysts in the gold-catalyzed phenol synthesis. (Figure presented.).
Tetracoordinate borates as catalysts for reductive formylation of amines with carbon dioxide
Du, Chen-Xia,Huang, Zijun,Jiang, Xiaolin,Li, Yuehui,Makha, Mohamed,Wang, Fang,Zhao, Dongmei
supporting information, p. 5317 - 5324 (2020/09/17)
We report sodium trihydroxyaryl borates as the first robust tetracoordinate organoboron catalysts for reductive functionalization of CO2. These catalysts, easily synthesized from condensing boronic acids with metal hydroxides, activate main group element-hydrogen (E-H) bonds efficiently. In contrast to BX3 type boranes, boronic acids and metal-BAr4 salts, under transition metal-free conditions, sodium trihydroxyaryl borates exhibit high reactivity of reductive N-formylation toward a variety of amines (106 examples), including those with functional groups such as ester, olefin, hydroxyl, cyano, nitro, halogen, MeS-, ether groups, etc. The over-performance to catalyze formylation of challenging pyridyl amines affords a promising alternative method to the use of traditional formylation reagents. Mechanistic investigation supports electrostatic interactions as the key for Si/B-H activation, enabling alkali metal borates as versatile catalysts for hydroborylation, hydrosilylation, and reductive formylation/methylation of CO2.
A NHC-silyliumylidene cation for catalytic N?formylation of amines using carbon dioxide
Leong, Bi-Xiang,Teo, Yeow-Chuan,Condamines, Cloe,Yang, Ming-Chung,Su, Ming-Der,So, Cheuk-Wai
, p. 14824 - 14833 (2020/12/21)
This study describes the use of a silicon(II) complex, namely, the NHC-silyliumylidene cation complex [(IMe)2SiH]I (1, IMe =:C{N(Me)C(Me)}2), to catalyze the chemoselective N-formylation of primary and secondary amines using CO2 and PhSiH3 under mild conditions to afford the corresponding formamides as a sole product (average reaction time: 4.5 h; primary amines, average yield: 95%, average TOF: 8 h?1; secondary amines, average yield: 98%, average TOF: 17 h?1). The activity of 1 and product yields outperform the currently available non-transition-metal catalysts used for this catalysis. Mechanistic studies show that the silicon(II) center in complex 1 catalyzes the C?N bond formation via a different pathway in comparison with non-transition-metal catalysts. It sequentially activates CO2, PhSiH3, and amines, which proceeds via a dihydrogen elimination mechanism, to form formamides, siloxanes, and dihydrogen gas.
Photophysical processes in rhenium(I) diiminetricarbonyl arylisocyanides featuring three interacting triplet excited states
Favale, Joseph M.,Danilov, Evgeny O.,Yarnell, James E.,Castellano, Felix N.
supporting information, p. 8750 - 8762 (2019/08/20)
We present a series of four transition-metal complexes based on the rhenium(I) tricarbonyl 1,10-phenanthroline (phen) template, with a lone ancillary arylisocyanide (CNAr) ligand to yield metal-organic chromophores of the generic molecular formula [Re(phen)-(CO)3(CNAr)]+ [CNAr = 2,6-diisopropylphenyl isocyanide (1), 4-phenyl-2,6-diisopropylphenyl isocyanide (2), 4-phenylethynyl-2,6-diisopropylphenyl isocyanide (3), and 4-biphenyl-2,6-diisopropylphenyl isocyanide (4)]. This particular series features varied degrees of π-conjugation length in the CNAr moiety, resulting in significant modulation in the resultant photophysical properties. All molecules possess long-lived [8- 700 μs at room temperature (RT)], strongly blue-green photoluminescent and highly energetic excited states λmax,em = 500-518 nm; Φ = 14-64%). Each of these chromophores has been photophysically investigated using static and dynamic spectroscopic techniques, the latter probed from ultrafast to suprananosecond time scales using transient absorption and photoluminescence (PL). Time-resolved PL intensity decays recorded as a function of the temperature were consistent with the presence of at least two emissive states lying closely spaced in energy with a third nonemissive state lying much higher in energy and likely ligand-field in character. The combined experimental evidence, along with the aid of electronic structure calculations (density functional theory and time-dependent density functional theory performed at the M06/Def2-SVP/SDD level), illustrates that the CNAr ligand is actively engaged in manipulating the excited-state decay in three of these molecules (2-4), wherein the triplet metal-to-ligand charge-transfer (3MLCT) state along with two distinct triplet ligand-centered (3LC) excited-state configurations (phen and CNAr) conspire to produce the resultant photophysical properties. Because the π conjugation within the CNAr ligand was extended, an interesting shift in the dominant photophysical processes was observed. When the CNAr conjugation length is short, as in 1, the phenanthroline 3LC state dominates, resulting in a configurationally mixed triplet excited state of both LC and MLCT character. With more extended π conjugation in the CNAr subunit (2-4), the initially generated 3LC(phen)/3MLCT excited state ultimately migrates to the CNAr 3LC state on the order of tens of picoseconds. Molecules 3 and 4 in this series also feature unique examples of inorganic excimer formation, as evidenced by dynamic self-quenching in the corresponding PL intensity decays accompanied by the observation of a short-lived low-energy emission feature.
Palladium-Catalyzed Diarylation of Isocyanides with Tetraarylleads for the Selective Synthesis of Imines and α-Diimines
Tran, Cong Chi,Kawaguchi, Shin-Ichi,Kobiki, Yohsuke,Matsubara, Hitomi,Tran, Dat Phuc,Kodama, Shintaro,Nomoto, Akihiro,Ogawa, Akiya
, p. 11741 - 11751 (2019/10/02)
Using tetraaryllead compounds (PbAr4) as arylating reagents, isocyanides undergo selective diarylation in the presence of palladium catalysts such as Pd(OAc)2 or Pd(PPh3)4 to afford imines and/or α-diimines based on the isocyanide employed. With aliphatic isocyanides, imines are obtained preferentially, whereas α-diimines are formed in the case of electron-rich aromatic isocyanides. The differences in imine/α-diimine selectivity can be attributed to the stability of imidoylpalladium intermediates formed in this catalytic reaction. Compared with other arylating reagents, tetraaryllead compounds are excellent candidates for use in the selective transformations to imines and/or α-diimines, especially in terms of inhibiting the oligomerization of isocyanides, which results in a lower product selectivity in many transition-metal-catalyzed reactions of isocyanides.
Diverse catalytic reactivity of a dearomatized PN3P?-nickel hydride pincer complex towards CO2 reduction
Li, Huaifeng,Gon?alves, Théo P.,Zhao, Qianyi,Gong, Dirong,Lai, Zhiping,Wang, Zhixiang,Zheng, Junrong,Huang, Kuo-Wei
supporting information, p. 11395 - 11398 (2018/10/20)
A dearomatized PN3P?-nickel hydride complex has been prepared using an oxidative addition process. The first nickel-catalyzed hydrosilylation of CO2 to methanol has been achieved, with unprecedented turnover numbers. Selective methylation and formylation of amines with CO2 were demonstrated by such a PN3P?-nickel hydride complex, highlighting its versatile functions in CO2 reduction.
Porous Organic Polymers with Built-in N-Heterocyclic Carbenes: Selective and Efficient Heterogeneous Catalyst for the Reductive N-Formylation of Amines with CO2
Lv, Hui,Wang, Wenlong,Li, Fuwei
, p. 16588 - 16594 (2018/10/24)
A series of porous organic polymers (POPs) based on N-heterocyclic carbene (NHC) building blocks has been prepared through an octacarbonyldicobalt complex [Co2(CO)8]-catalyzed trimerization of terminal alkyne groups. By changing the monomer ratio in the copolymerization, cross-linked POPs with tunable surface areas of 485–731 m2 g?1 and pore volumes of 0.31–0.51 cm3 g?1 were easily prepared. Compared with the analogues homogeneous NHC (SIPr) catalysts, the POPs exhibited an enhanced catalytic activity and high selectivity in the reductive functionalization of CO2 with amines. The extraordinary performance of the sample could be attributed to the combination of the gas enrichment (or storage) effect, enhanced in-pore concentrations of other substrates, and advantageous micropore structures of the porous polymers. Meanwhile, these catalysts can easily be separated and recycled from the reaction systems with only a slight loss of activity. This excellent catalytic performance and facile recycling of heterogeneous catalysts make them very attractive. These NHC-containing POPs may provide a new platform for catalytic transformations of CO2.
Synthesis and structure elucidation of allyl Pd(II) complexes of NHC ligands derived from substituted imidazo[1,5-a]quinolin-1(2H)-ylidene
Lyapchev, Rumen,Petrov, Petar,Dangalov, Miroslav,Vassilev, Nikolay G.
, p. 194 - 209 (2017/10/09)
Nine Pd(II) complexes involving N-heterocyclic carbenes (NHCs) derived from 2-substituted and 2- and 7-substituted imidazo[1,5-a]quinolin-1(2H)-ylidene with auxiliary allylic ligands were synthesized and characterized. The structure and configuration of the complexes were elucidated on the basis of combination of dynamic NMR and DFT studies. Conformational studies in respect of hindered rotation around Pd-C bond and η3-η1-η3 pseudo allyl rotation were performed. The results from dynamic NMR and DFT studies confirmed the mechanism of selective η3-η1-η3 isomerization, whose energy barriers are affected by steric hindrance of substituents at nitrogen atom. Energy barriers of isomerization (16.7–18.8 kcal/mol) are slightly influenced by the electronic nature of substituents at seventh position in imidazo[1,5-a]quinolin-1(2H)-ylidene moiety. The results from DFT calculations were in good agreement with the experimental energy barriers.
Catalyst-free: N -formylation of amines using BH3NH3 and CO2 under mild conditions
Zhao, Tian-Xiang,Zhai, Gao-Wen,Liang, Jian,Li, Ping,Hu, Xing-Bang,Wu, You-Ting
supporting information, p. 8046 - 8049 (2017/07/22)
The catalyst-free N-formylation of amines using CO2 as the C1 source and BH3NH3 as the reductant has been developed for the first time. The corresponding formylated products of both primary and secondary amines are obtained in good to excellent yields (up to 96% of isolated yield) under mild conditions.
Electrostatic Catalyst Generated from Diazadiborinine for Carbonyl Reduction
Wu, Di,Wang, Ruixing,Li, Yongxin,Ganguly, Rakesh,Hirao, Hajime,Kinjo, Rei
supporting information, p. 134 - 151 (2017/07/17)
Since the seminal discovery by van der Waals in the late 19th century that weak attractive forces exist between even electrically neutral atoms or molecules, a number of noncovalent interactions have been recognized. Among them, electrostatic interactions such as hydrogen bonds play pivotal roles in countless chemical processes and biochemical living systems. By mimicking biocatalysis, various organocatalysts equipped with hydrogen-bond functionality have been developed; however, a challenge has persisted in designing catalysts exploiting other types of noncovalent interactions. Here, we report metal-free hydroboration reactions of carbonyl compounds and CO2 catalyzed by aromatic diazadiborinine. A joint experimental and computational study on the reaction mechanism suggests that adducts of diazadiborinine with carbonyl and CO2 formed at the initial stage of the reactions serve as actual catalysts. The former stabilizes the transition state by using the electrostatic interaction between the hydride of borane and the polar, hole-shaped structure of the adduct.
