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1.
Sequential treatment of 2‐C6H4Br(CHO) with LiC≡CR1 (R1=SiMe3, tBu), nBuLi, CuBr?SMe2 and HC≡CCHClR2 [R2=Ph, 4‐CF3Ph, 3‐CNPh, 4‐(MeO2C)Ph] at ?50 °C leads to formation of an intermediate carbanion (Z)‐1,2‐C6H4{CA(=O)C≡CBR1}{CH=CH(CH?)R2} ( 4 ). Low temperatures (?50 °C) favour attack at CB leading to kinetic formation of 6,8‐bicycles containing non‐classical C‐carbanion enolates ( 5 ). Higher temperatures (?10 °C to ambient) and electron‐deficient R2 favour retro σ‐bond C?C cleavage regenerating 4 , which subsequently closes on CA providing 6,6‐bicyclic alkoxides ( 6 ). Computational modelling (CBS‐QB3) indicated that both pathways are viable and of similar energies. Reaction of 6 with H+ gave 1,2‐dihydronaphthalen‐1‐ols, or under dehydrating conditions, 2‐aryl‐1‐alkynylnaphthlenes. Enolates 5 react in situ with: H2O, D2O, I2, allylbromide, S2Me2, CO2 and lead to the expected C ‐E derivatives (E=H, D, I, allyl, SMe, CO2H) in 49–64 % yield directly from intermediate 5 . The parents (E=H; R1=SiMe3, tBu; R2=Ph) are versatile starting materials for NaBH4 and Grignard C=O additions, desilylation (when R1=SiMe) and oxime formation. The latter allows formation of 6,9‐bicyclics via Beckmann rearrangement. The 6,8‐ring iodides are suitable Suzuki precursors for Pd‐catalysed C?C coupling (81–87 %), whereas the carboxylic acids readily form amides under T3P® conditions (71–95 %).  相似文献   

2.
The synthesis and reactivity of a CoI pincer complex [Co(?3P,CH,P‐P(CH)PNMeiPr)(CO)2]+ featuring an η2‐ Caryl?H agostic bond is described. This complex was obtained by protonation of the CoI complex [Co(PCPNMeiPr)(CO)2]. The CoIII hydride complex [Co(PCPNMeiPr)(CNtBu)2(H)]+ was obtained upon protonation of [Co(PCPNMeiPr)(CNtBu)2]. Three ways to cleave the agostic C?H bond are presented. First, owing to the acidity of the agostic proton, treatment with pyridine results in facile deprotonation (C?H bond cleavage) and reformation of [Co(PCPNMeiPr)(CO)2]. Second, C?H bond cleavage is achieved upon exposure of [Co(?3P,CH,P‐P(CH)PNMeiPr)(CO)2]+ to oxygen or TEMPO to yield the paramagnetic CoII PCP complex [Co(PCPNMeiPr)(CO)2]+. Finally, replacement of one CO ligand in [Co(?3P,CH,P‐P(CH)PNMeiPr)(CO)2]+ by CNtBu promotes the rapid oxidative addition of the agostic η2‐Caryl?H bond to give two isomeric hydride complexes of the type [Co(PCPNMeiPr)(CNtBu)(CO)(H)]+.  相似文献   

3.
The electronically unsaturated dirhenium complex [Re2(CO)8(μ‐H)(μ‐Ph)] ( 1 ) has been found to exhibit aromatic C?H activation upon reaction with N,N‐diethylaniline, naphthalene, and even [D6]benzene to yield the compounds [Re2(CO)8(μ‐H)(μ‐η1‐NEt2C6H4)] ( 2 ), [Re2(CO)8(μ‐H)(μ‐η2‐1,2‐C10H7)] ( 3 ), and [D6]‐ 1 , respectively, in good yields. The mechanism has been elucidated by using DFT computational analyses, and involves a binuclear C?H bond‐activation process.  相似文献   

4.
[LCRP((PhP)2C2H4)][OTf] ( 4 a,b [OTf]) and [LCiPrP(PPh2)2][OTf] ( 5 b [OTf]) were prepared from the reaction of imidazoliumyl‐substituted dipyrazolylphosphane triflate salts [LCRP(pyr)2][OTf] ( 3 a,b [OTf]; a : R=Me, b =iPr; LCR=1,3‐dialkyl‐4,5‐dimethylimidazol‐2‐yl; pyr=3,5‐dimethylpyrazol‐1‐yl) with the secondary phosphanes PhP(H)C2H4P(H)Ph) and Ph2PH. A stepwise double P?N/P?P bond metathesis to catena‐tetraphosphane‐2,3‐diium triflate salt [(Ph2P)2(LCMeP)2][OTf]2 ( 7 a [OTf]2) is observed when reacting 3 a [OTf] with diphosphane P2Ph4. The coordination ability of 5 b [OTf] was probed with selected coinage metal salts [Cu(CH3CN)4]OTf, AgOTf and AuCl(tht) (tht=tetrahydrothiophene). For AuCl(tht), the helical complex [{(Ph2PPLCiPr)Au}4][OTf]4 ( 9 [OTf]4) was unexpectedly formed as a result of a chloride‐induced P?P bond cleavage. The weakly coordinating triflate anion enables the formation of the expected copper(I) and silver(I) complexes [( 5 b )M(CH3CN)3][OTf]2 (M=Cu, Ag) ( 10 [OTf]2, 11 [OTf]2).  相似文献   

5.
Strongly electron withdrawing cyanoolefins tetracyanoethylene (tcne) and 7,7,8,8-tetracyano-p-quinodimethane (tcnq) react with [(η5-C5Me5)MCl(MDMPP-P,O)] (M=Rh, Ir; MDMPP-P,O=PPh2(2-O-6-MeO-C6H3), a P,O chelating phosphane) by insertion into the C−H bond adjacent to the M−O σ bond. The crystal structure of the iridium complex formed upon insertion of tcne is shown.  相似文献   

6.
The synthesis and reactivity of a CoI pincer complex [Co(ϰ3P,CH,P‐P(CH)PNMeiPr)(CO)2]+ featuring an η2‐ Caryl−H agostic bond is described. This complex was obtained by protonation of the CoI complex [Co(PCPNMeiPr)(CO)2]. The CoIII hydride complex [Co(PCPNMeiPr)(CNtBu)2(H)]+ was obtained upon protonation of [Co(PCPNMeiPr)(CNtBu)2]. Three ways to cleave the agostic C−H bond are presented. First, owing to the acidity of the agostic proton, treatment with pyridine results in facile deprotonation (C−H bond cleavage) and reformation of [Co(PCPNMeiPr)(CO)2]. Second, C−H bond cleavage is achieved upon exposure of [Co(ϰ3P,CH,P‐P(CH)PNMeiPr)(CO)2]+ to oxygen or TEMPO to yield the paramagnetic CoII PCP complex [Co(PCPNMeiPr)(CO)2]+. Finally, replacement of one CO ligand in [Co(ϰ3P,CH,P‐P(CH)PNMeiPr)(CO)2]+ by CNtBu promotes the rapid oxidative addition of the agostic η2‐Caryl−H bond to give two isomeric hydride complexes of the type [Co(PCPNMeiPr)(CNtBu)(CO)(H)]+.  相似文献   

7.
Water‐soluble arene–ruthenium complexes coordinated with readily available aniline‐based ligands were successfully employed as highly active catalysts in the C?H bond activation and arylation of 2‐phenylpyridine with aryl halides in water. A variety of (hetero)aryl halides were also used for the ortho‐C?H bond arylation of 2‐phenylpyridine to afford the corresponding ortho‐ monoarylated products as major products in moderate to good yields. Our investigations, including time‐scaled NMR spectroscopy and mass spectrometry studies, evidenced that the coordinating aniline‐based ligands, having varying electronic and steric properties, had a significant influence on the catalytic activity of the resulting arene–ruthenium–aniline‐based complexes. Moreover, mass spectrometry identification of the cycloruthenated species, {(η6‐arene)Ru(κ2C,N‐phenylpyridine)}+, and several ligand‐coordinated cycloruthenated species, such as [(η6‐arene)Ru(4‐methylaniline)(κ2C,N‐phenylpyridine)]+, found during the reaction of 2‐phenylpyridine with the arene–ruthenium–aniline complexes further authenticated the crucial roles of these species in the observed highly active and tuned catalyst. At last, the structures of a few of the active catalysts were also confirmed by single‐crystal X‐ray diffraction studies.  相似文献   

8.
Treatment of Ru3(CO)12 with an equivalent of (2‐phenyl‐1H ‐inden‐3‐yl)dicyclohexylphosphine ( 1 ) and (2‐pyridyl‐1H ‐inden‐1‐yl)dicyclohexylphosphine ( 4 ) in refluxing heptane gave the novel trinuclear ruthenium clusters (μ3‐η125–2‐phenyl‐3‐Cy2PC9H4)Ru3(CO)8 ( 1c ) and [μ2‐η1–2‐(pyridin‐2‐yl)‐3‐Cy2PC9H6]Ru3(CO)9 ( 4a ), respectively, via C ─ H bond cleavage. (2‐Mesityl‐1H ‐inden‐3‐yl)dicyclohexylphosphine ( 2 ) reacted with Ru3(CO)12 in refluxing heptane to give the trinuclear ruthenium cluster [μ‐2‐mesityl‐(3‐Cy2PC9H5)](μ2‐CO)Ru3(CO)9 ( 2c ) via C ─ H bond cleavage and carbonyl insertion. 2‐(Anthracen‐9‐yl)‐1H –inden‐3‐yldicyclohexylphosphine ( 3 ) reacted with Ru3(CO)12 in refluxing heptane to give the dinuclear ruthenium cluster [μ2‐η33–2‐(anthracen‐9‐yl)‐3‐Cy2PC9H6]Ru2(CO)5 ( 3a ). The structures of 1c , 2c , 3a and 4a were fully characterized using IR and NMR spectroscopy, elemental analysis and single‐crystal X‐ray diffraction. These results suggest that the 2‐aryl substituent on the indenyl ring has a pronounced effect on the reaction and coordination modes of Ru3(CO)12.  相似文献   

9.
The ferrocene derivative (η5‐Cp)Fe{η5‐C5H3‐1‐(ArNCH)‐2‐(CH2NMe2)} ( 1 ; Ar=2,6‐iPr2C6H3)) reacts diastereoselectively with LiR by carbolithiation and subsequent hydrolysis to give (η5‐Cp)Fe{η5‐C5H3‐1‐(ArHNCHR)‐2‐(CH2NMe2)} ( 3 : R=tBu; 4 : R=Ph; 5 : R=Me) in high yields. For R=tBu, the organolithium derivative (η5‐Cp)Fe{η5‐C5H3‐1‐(ArLiNCHR)‐2‐(CH2NMe2)} ( 2 ) was isolated. Compound 2 reacts with GeCl2?dioxane and SnCl2 to give the metallylene amide chlorides (η5‐Cp)Fe{η5‐C5H3‐1‐(ArMNCHtBu)‐2‐(CH2NMe2)} 6 (M=GeCl) and 7 (M=SnCl), respectively, which each contain three stereogenic centers. The potential of 7 as a ligand in transition‐metal chemistry is demonstrated by formation of its complex (η5‐Cp)Fe{η5‐C5H3‐1‐(ArMNCHtBu)‐2‐(CH2NMe2)} [ 9 , M= Sn(Cl)W(CO)5]. Treatment of 3 with tert‐butyllithium at room temperature causes an unprecedented carbon–carbon bond cleavage whereas under kinetic control, lithiation at the Cp‐3 position takes place, which leads to the isolation of (η5‐Cp)Fe{η5‐C5H3‐1‐(ArHNCHtBu)‐2‐(CH2NMe2)‐3‐SiMe3} ( 10 ).  相似文献   

10.
A cyclic (alkyl)(amino)carbene (CAAC) was found to undergo unprecedented rearrangements and transformations of its core structure in the presence of Group 1 and 2 metals. Although the carbene was also found to be prone to intramolecular C?H activation, it was competent for intermolecular activation of a variety of sp‐, sp2‐, and sp3‐hybridized C?H bonds. Double C?F activation of hexafluorobenzene was also observed in this work. These processes all hold relevance to the role of these carbenes in catalysis, as well as to their use in the synthesis of new and unusual main group or transition metal complexes.  相似文献   

11.
The potential of homogeneous oxidation catalysis employing bromine has remained largely unexplored. We herein show that the combination of a tetraalkylammonium bromide and meta‐chloroperbenzoic acid offers a unique catalyst system for the convenient and selective oxidation of saturated C(sp3)−H bonds upon photochemical initiation with day light. This approach enables remote, intramolecular, position‐selective C−H amination as demonstrated for 20 different examples. For the first time, an N‐halogenated intermediate was isolated as the active catalyst state in a catalytic Hofmann–Löffler reaction. In addition, an expeditious one‐pot synthesis of N‐sulfonyl oxaziridines from N‐sulfonamides was developed and exemplified for 15 transformations. These pioneering examples provide a change in paradigm for molecular catalysis with bromine.  相似文献   

12.
A set of calcium and barium complexes containing the fluoroarylamide N(C6F5)2 is presented. These compounds illustrate the key role of stabilising M⋅⋅⋅F−C secondary interactions in the construction of low-coordinate alkaline earth complexes. The nature of Ca⋅⋅⋅F−C bonding in calcium complexes is examined in the light of structural data, bond valence sum (BVS) analysis and DFT computations. The molecular structures of [Ca{N(C6F5)2}2(Et2O)2] ( 4 ′), [Ca{μ-N(SiMe3)2}{N(C6F5)2}]2 ( 52 ), [Ba{μ-N(C6F5)2}{N(C6F5)2}⋅toluene]2 ( 62 ), [{BDIDiPP}CaN(C6F5)2]2 ( 72 ), [{N^NDiPP}CaN(C6F5)2]2 ( 82 ), and [Ca{μ-OB(CH(SiMe3)2)2}{N(C6F5)2}]2 ( 92 ), where {BDIDiPP} and {N^NDiPP} are the bidentate ligands CH[C(CH3)NDipp]2 and DippNC6H4CNDipp (Dipp=2,6-iPr2-C6H3), are detailed. Complex 62 displays strong Ba⋅⋅⋅F−C contacts at around 2.85 Å. The calcium complexes feature also very short intramolecular Ca−F interatomic distances at around 2.50 Å. In addition, the three-coordinate complexes 72 and 82 form dinuclear structures due to intermolecular Ca⋅⋅⋅F−C contacts. BVS analysis shows that Ca⋅⋅⋅F−C interactions contribute to 15–20 % of the bonding pattern around calcium. Computations demonstrate that Ca⋅⋅⋅F−C bonding is mostly electrostatic, but also contains a non-negligible covalent contribution. They also suggest that Ca⋅⋅⋅F−C are the strongest amongst the range of weak Ca⋅⋅⋅X (X=F, H, Cπ) secondary interactions, due to the high positive charge of Ca2+ which favours electrostatic interactions.  相似文献   

13.
Starting from Ph3SiH, the barium precatalyst Ba[CH(SiMe3)2]2?(THF)3 was used to produce the disilazane Ph3SiN(Bn)SiPh2NHBn ( 4 ) by sequential N?H/H?Si dehydrogenative couplings with BnNH2 and Ph2SiH2. Substrate scope was extended to other amines and hydrosilanes. This smooth protocol gives quantitative yields and full chemoselectivity. Compound 4 and the intermediates Ph3SiNHBn and Ph3SiN(Bn)SiHPh2 were structurally characterised. Further attempts at chain extension by dehydrocoupling of Ph2SiH2 with 4 instead resulted in cyclisation of this compound, forming the cyclodisilazane c‐(Ph2Si‐NBn)2 ( 5 ) which was crystallographically authenticated. The ring‐closure mechanism leading to 5 upon release of C6H6 was determined by complementary experimental and theoretical (DFT) investigations. Ba[CH(SiMe3)2]2?(THF)3 and 4 react to afford the reactive Ba{N(Bn)SiPh2N(Bn)SiPh3}2, which was characterised in situ by NMR spectroscopy. Next, in a stepwise process, intramolecular nucleophilic attack of the metal‐bound amide on the terminal silicon atom generates a five‐coordinate silicate. It is followed by turnover‐limiting β‐C6H5 transfer to barium; this releases 5 and forms a transient [Ba]?Ph species, which undergoes aminolysis to regenerate [Ba]?N(Bn)SiPh2N(Bn)SiPh3. DFT computations reveal that the irreversible production of 5 through such a stepwise ring‐closure mechanism is much more kinetically facile (ΔG=26.2 kcal mol?1) than an alternative σ‐metathesis pathway (ΔG=48.2 kcal mol?1).  相似文献   

14.
Unusual cleavage of P?C and C?H bonds of the P2N2 ligand, in heteroleptic [Ni(P2N2)(diphosphine)]2+ complexes under mild conditions, results in the formation of an iminium formyl nickelate featuring a C,P,P‐tridentate coordination mode. The structures of both the heteroleptic [Ni(P2N2)(diphosphine)]2+ complexes and the resulting iminium formyl nickelate have been characterized by NMR spectroscopy and single‐crystal X‐ray diffraction analysis. Density functional theory (DFT) calculations were employed to investigate the mechanism of the P?C/C?H bond cleavage, which involves C?H bond cleavage, hydride rotation, Ni?C/P?H bond formation, and P?C bond cleavage.  相似文献   

15.
The Ni‐catalyzed C(sp2)?H/C(sp3)?H coupling of benzamides with toluene derivatives was recently successfully achieved with mild oxidant iC3F7I. Herein, we employ density functional theory (DFT) methods to resolve the mechanistic controversies. Two previously proposed mechanisms are excluded, and our proposed mechanism involving iodine‐atom transfer (IAT) between iC3F7I and the NiII intermediate was found to be more feasible. With this mechanism, the presence of a carbon radical is consistent with the experimental observation that (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) completely quenches the reaction. Meanwhile, the hydrogen‐atom abstraction of toluene is irreversible and the activation of the C(sp2)?H bond of benzamides is reversible. Both of these conclusions are in good agreement with Chatani's deuterium‐labeling experiments.  相似文献   

16.
Site‐selective C−H functionalization of aliphatic alkyl chains is a longstanding challenge in oxidation catalysis, given the comparable relative reactivity of the different methylenes. A supramolecular, bioinspired approach is described to address this challenge. A Mn complex able to catalyze C(sp3)‐H hydroxylation with H2O2 is equipped with 18‐benzocrown‐6 ether receptors that bind ammonium substrates via hydrogen bonding. Reversible pre‐association of protonated primary aliphatic amines with the crown ether selectively exposes remote positions (C8 and C9) to the oxidizing unit, resulting in a site‐selective oxidation. Remarkably, such control of selectivity retains its efficiency for a whole series of linear amines, overriding the intrinsic reactivity of C−H bonds, no matter the chain length.  相似文献   

17.
The reaction of [Pd(CH3CN)2Cl2] with N ‐functional group‐substituted 2‐iminomethylpyrrole‐based ligands, namely N 1‐((1H‐pyrrol‐2‐yl)methylene)‐N 3,N 3‐dimethylpropane‐1,3‐diamine (LA), N 1‐((1H‐pyrrol‐2‐yl)methylene)‐N 3‐methyl‐N 3‐phenylpropane‐1,3‐diamine (LB), N ‐((1H‐pyrrol‐2‐yl)methylene)‐3‐(methylthio)propan‐1‐amine (LC) and N ‐((1H‐pyrrol‐2‐yl)methylene)‐3‐methoxypropan‐1‐amine (LD), resulted in [Ln PdCl] (Ln  = LA–LD) complexes in high yield via N─H bond activation of pyrrole moiety without use of base. [Ln PdCl] existed as monomeric four‐coordinated complexes with slightly distorted square planar geometries around the palladium metal center. The ligands show N ,N ′,X ‐tridentate binding mode to the palladium metal center to give two fused ring metallacycles. [LBPdCl] gave the highest activity (3.29 × 105 g PMMA (mol Pd)−1 h−1) for a methyl methacrylate (MMA) polymerization in the presence of modified methylaluminoxane at 60 °C compared to the other Pd(II) analogues, and resulted in PMMA with higher molecular weight (M w = 7.16 × 105 g mol−1) and narrower polydispersity index. Syndiotactic‐enriched PMMA resulted in all cases.  相似文献   

18.
The cyclization of substituted N‐methoxy benzamides with alkynes in the presence of an easily affordable cobalt complex and NaOAc provides isoquinolone derivatives in good to excellent yields. The cyclization reaction is compatible with a range of functional group‐substituted benzamides, as well as ester‐ and alcohol‐substituted alkynes. The cobalt complex [CoIIICp*(OR)2] (R=Me or Ac) serves as an efficient catalyst for the cyclization reaction. Later, isoquinolone derivatives were converted into 1‐chloro and 1‐bromo substituted isoquinoline derivatives in excellent yields in the presence of POCl3 or PBr3.  相似文献   

19.
Efficiency and structural specificity earmark the reaction of phosphonium ions 1 with cyclic acetals and ketals to yield 1,3,2‐dioxaphospholanium ions 2 [Eq. (1)]. Potential applications of this reaction are in monitoring trace levels of organophosphorus esters and in developing novel carbonyl deprotection agents. R=OCH3, CH3; R1=H, CH3; R2=CH3, C6H5; R3=H, CH3.  相似文献   

20.
C−C coupling by transition metal catalyzed C−H activation has developed into a diverse area of research. The applicable catalysts are manifold, and the variety of products obtained range from basic chemicals to pharmaceuticals and building blocks for carbon networks. One reaction, in which several C−C bonds are formed under C−H activation of a methyl group, is the conversion of ortho-iodoanisole according to Equation (1).  相似文献   

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