Experimental and DFT Studies Explain Solvent Control of C–H Activation and Product Selectivity in the Rh(III)-Catalyzed Formation of Neutral and Cationic Heterocycles

Davies, David; Ellul, Charles E.; Macgregor, Stuart A.; McMullin, Claire L.; Singh, Kuldip

doi:10.1021/jacs.5b04858

Cited by 111 publications

(73 citation statements)

References 49 publications

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“…Within the field of directed CÀHa ctivation of N-heterocycles and annulated cationic N-heterocycles formation, Rh III -catalyzed CÀHa ctivation and annulation reactions of 1-phenyl-1H-pyrazoles and alkynes were developed by Davies and Macgregor et al [70] [RhCp*Cl 2 ] 2 /Cu(OAc) 2 ·H 2 O/KPF 6 was used as the catalyst system,and the reactionwas dependent on the substrates, solvent, andr eactionc onditions (Scheme 32). Furthermore,t he authors'e xperimental and DFT studies revealed that more polar solvents favored cationic CÀNc oupled products,w hile low polarity solvents resultedi nC ÀCc oupled products.…”

Section: Synthesis Of Pyrazolocinnolinium Saltsmentioning

confidence: 99%

Advancements in the Synthesis and Applications of Cationic N‐Heterocycles through Transition Metal‐Catalyzed C−H Activation

Gandeepan

2015

Chemistry An Asian Journal

125

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Cationic N-heterocycles are an important class of organic compounds largely present in natural and bioactive molecules. They are widely used as fluorescent dyes for biological studies, as well as in spectroscopic and microscopic methods. These compounds are key intermediates in many natural and pharmaceutical syntheses. They are also a potential candidate for organic light-emitting diodes (OLEDs). Because of these useful applications, the development of new methods for the synthesis of cationic N-heterocycles has received a lot of attention. In particular, many C-H activation methodologies that realize high step- and atom-economies toward these compounds have been developed. In this review, recent advancements in the synthesis and applications of cationic N-heterocycles through C-H activation reactions are summarized. The new C-H activation reactions described in this review are preferred over their classical analogs.

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Section: Synthesis Of Pyrazolocinnolinium Saltsmentioning

confidence: 99%

Advancements in the Synthesis and Applications of Cationic N‐Heterocycles through Transition Metal‐Catalyzed C−H Activation

Gandeepan

2015

Chemistry An Asian Journal

125

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“…Recently, insertion reactions of alkynes into transition metal–carbon bonds have attracted considerable attention in the field of organometallic chemistry, especially for the M–C bond (M = Ir, Rh) in five‐membered N‐containing or P‐containing cyclometalated complexes . This situation might be due to the following two factors: firstly, the diversity of insertion mode of alkynes into M–C bond results in the various products with novel structures and interesting chemistry, including 1,2‐insertion,, , 1,1‐insertion,[4a, b], , and subsequent structural transformation; secondly, in many organic reactions involving alkynes catalyzed by transition metal complexes, the step of alkyne insertion into M–C bond plays an integral part in the catalytic cycle, therefore, detailed study on the reactivity of alkyne insertion into different M–C bonds would be very useful for understanding catalytic mechanism and designing new catalytic processes. Although insertion reactions of alkynes into M–C bond in five‐membered cyclometalated complexes have been intensively studied,, the similar reactions with that in six‐membered cyclometalated complexes have hardly been reported .…”

Section: Resultsmentioning

confidence: 99%

Reactivity of Alkyne Insertion and Catalytic Activity of Five‐ and Six‐Membered Cyclometalated Phosphine Complexes of Iridium

Wang

et al. 2018

Eur J Inorg Chem

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Reactions of three aryl-substituted phosphines with [Cp*IrCl 2 ] 2 afforded the corresponding five-membered or sixmembered cyclometalated iridium complexes (2 or 5,6) via an intramolecular C(sp 2 )-H bond activation. Insertion reactions of the five-membered cycloiridated complex 2 with PhC≡CPh and PhC≡CCOPh resulted in the corresponding five-membered and six-membered doubly cycloiridated complexes 7 and 8, the formation of which presumably went through the vinylidene rearrangement of alkynes followed by 1,1-insertion; while the reactions of the six-membered cyclometalated complexes 5, 6 [a] 3195 with PhC≡CPh or PhC≡CCOPh gave the corresponding eightmembered cycloiridated complexes 9-12 by 1,2-insertion. The hydrosilylation of imines catalyzed by five-or six-membered P-containing cycloiridated complexes were studied, and the results proved that the six-membered cycloiridated complex 5 can be used as an efficient catalyst, which was applied for the hydrosilylation of various imines, especially aldimines. Molecular structures of complexes 9, 10 and 12 were determined by X-ray diffraction. Results and Discussion Reaction of [Cp*IrCl 2 ] 2 with Benzyldiphenylphosphine (1)Reaction of [Cp*IrCl 2 ] 2 with benzyldiphenylphosphine in the presence of sodium acetate at room temperature result in the expected five-membered cyclometalated complex 2 in the yield of 62 % (Scheme 1). Obviously, the formation of complex 2 involves an intramolecular C(sp 2 )-H bond activation. The 1 H NMR spectrum of 2 showed several groups of multiplets in the aromatic region, all integrating to 14 H due to the phenyl rings, two doublets at δ = 3.92 and 3.75 ppm assigned to signal for the methylene group, and a doublet at δ = 1.55 corresponding to five methyl groups of Cp*; the 31 P NMR spectrum exhibited a peak at δ = 32.81, which is consistent with the data (32.1) reported for the (1-naphthyl)diphenylphosphine analogue Cp*IrClPPh 2 (η 1 -C 10 H 6 ). [10] Scheme 1. Reaction of [Cp*IrCl 2 ] 2 with benzyldiphenylphosphine (1). Reactions of [Cp*IrCl 2 ] 2 with 2-(Diphenylphosphino)biphenyl (3) and 2-(Diisopropylphosphino)biphenyl (4)First, the phosphines 3 and 4 were chosen as ligands for the reason that they could provide a C(sp 2 )-H bond at the appropri-Full Paper ate position only for constructing the six-membered metallacycle. Similarly, reactions of [Cp*IrCl 2 ] 2 with ligands 3 and 4 in the presence of sodium acetate at room temperature resulted in the corresponding six-membered iridacycles 5 and 6 in high yields of 95 % and 94 % respectively (Scheme 2). The 1 H NMR spectrum of 6 showed six groups of peaks in the aromatic region, all integrating to 8 H due to the biphenyl unit, these resonances indicated that one aromatic C(sp 2 )-H bond is activated in the reaction to form the six-membered cyclometalated complex 6; the 31 P NMR spectrum exhibited a peak at δ = 9.28 ppm, which is significantly low-frequency shifted compared with the five-membered analogue.Scheme 2. Reactions of [Cp*IrCl 2 ] 2 with 2-(diphenylphosphino)biphenyl (3) and 2-(dii...

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“…Later,D avies,a nd Macgregor also developed similar salt formation methods from vinyl pyridines, phenylp yridines,a nd phenyl pyrazole with alkynesi nt he presence of RhCp*c atalyst. [88] Scheme46. Rh I or Co III -catalyzedsynthesis of quinolines from anilines.…”

Section: Quinoliziniumsaltsmentioning

confidence: 99%

Reaching Green: Heterocycle Synthesis by Transition Metal‐Catalyzed C−H Functionalization in Sustainable Medium

Santhoshkumar

Cheng

2019

Chemistry A European J

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Catalytic CÀHf unctionalization has emerged as an efficient alternative to traditional coupling reactions. However,s omeo ft hese reactions depend on environmentally harmful solvents, weakening the overall green nature of these methods. As organic processes consume large amount of solvents, the use of less harmful solvents enhance the sustainability of these reactions. Herein, we present an overview of transition metal-catalyzed CÀHf unctionalization reactions for the synthesis of heterocycles in sustainable solvents based on CHEM21 solvent selection guide.[a] Dr.

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Experimental and DFT Studies Explain Solvent Control of C–H Activation and Product Selectivity in the Rh(III)-Catalyzed Formation of Neutral and Cationic Heterocycles

Cited by 111 publications

References 49 publications

Advancements in the Synthesis and Applications of Cationic N‐Heterocycles through Transition Metal‐Catalyzed C−H Activation

Advancements in the Synthesis and Applications of Cationic N‐Heterocycles through Transition Metal‐Catalyzed C−H Activation

Reactivity of Alkyne Insertion and Catalytic Activity of Five‐ and Six‐Membered Cyclometalated Phosphine Complexes of Iridium

Reaching Green: Heterocycle Synthesis by Transition Metal‐Catalyzed C−H Functionalization in Sustainable Medium

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