- Rhodium-catalyzed reductive carbonylation of aryl iodides to arylaldehydes with syngas
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The reductive carbonylation of aryl iodides to aryl aldehydes possesses broad application prospects. We present an efficient and facile Rh-based catalytic system composed of the commercially available Rh salt RhCl3·3H2O, PPh3 as phosphine ligand, and Et3N as the base, for the synthesis of arylaldehydes via the reductive carbonylation of aryl iodides with CO and H2 under relatively mild conditions with a broad substrate range affording the products in good to excellent yields. Systematic investigations were carried out to study the experimental parameters. We explored the optimal ratio of Rh salt and PPh3 ligand, substrate scope, carbonyl source and hydrogen source, and the reaction mechanism. Particularly, a scaled-up experiment indicated that the catalytic method could find valuable applications in industrial productions. The low gas pressure, cheap ligand and low metal dosage could significantly improve the practicability in both chemical researches and industrial applications.
- Chen, Suqing,Liu, Zhenghui,Mu, Tiancheng,Wang, Peng,Yan, Zhenzhong,Yu, Dongkun,Zhao, Xinhui
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p. 645 - 656
(2020/05/14)
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- Visible-Light-Promoted Nickel- and Organic-Dye-Cocatalyzed Formylation Reaction of Aryl Halides and Triflates and Vinyl Bromides with Diethoxyacetic Acid as a Formyl Equivalent
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A simple formylation reaction of aryl halides, aryl triflates, and vinyl bromides under synergistic nickel- and organic-dye-mediated photoredox catalysis is reported. Distinct from widely used palladium-catalyzed formylation processes, this reaction proceeds by a two-step mechanistic sequence involving initial in situ generation of the diethoxymethyl radical from diethoxyacetic acid by a 4CzIPN-mediated photoredox reaction. The formyl-radical equivalent then undergoes nickel-catalyzed substitution reactions with aryl halides and triflates and vinyl bromides to form the corresponding aldehyde products. Significantly, besides aryl bromides, less reactive aryl chlorides and triflates and vinyl halides serve as effective substrates for this process. Since the mild conditions involved in this reaction tolerate a plethora of functional groups, the process can be applied to the efficient preparation of diverse aromatic aldehydes.
- Huang, He,Li, Xiangmin,Yu, Chenguang,Zhang, Yueteng,Mariano, Patrick S.,Wang, Wei
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supporting information
p. 1500 - 1505
(2017/02/05)
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- Acetamide/SO2Cl2 as an efficient reagent for Friedel-Craft's acylation of aromatic compounds under ultrasonic and microwave conditions
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Acetamide/SO2Cl2 reagent has been developed for effective Friedel-Craft's acylation of aromatic compounds. Acylation of aromatic compounds with acetamide/SO2Cl2 was much more effective and faster than analogous (acetamide/SOCl2) and (acetamide/POCl 3) reagents even under conventional conditions. However, microwave and ultrasonic assisted reactions afforded high yields of products in very short reaction times (30-40 min under sonication and 3-4 min under microwave assisted conditions).
- Satish Kumar, Mukka,Chinna Rajanna, Kamatala,Venkanna, Purugula,Venkateswarlu, Marri
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p. 1756 - 1759
(2014/03/21)
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- RuCl 3-DCHA catalyst system: A selective aerobic oxidation of primary benzylic alcohols under mild conditions
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The aerobic oxidation of benzylic alcohols to their corresponding aldehydes was performed in a RuCl3 · 3H2O-dicyclohexylamine (DCHA) catalyst system under ambient atmosphere at room temperature. It is noteworthy that the RuCl3 · 3H2O-DCHA system displayed a preference for the primary versus secondary benzylic alcohols in both intermolecular and intramolecular competition experiments.
- Yu, Kaihui,Ye, Dongnai,Shu, Lei,Zhang, Shiyong,Hu, Qiaosheng,Liu, Liangxian
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experimental part
p. 2318 - 2326
(2012/06/18)
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- Competition between azido cleavage and triplet nitrene formation in azidomethylacetophenones
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Photolysis of p- and m-azidomethylacetophenone (1a, 1b) in argon-saturated solutions yields predominantly imine 2a, 2b, whereas irradiation of 1a, 1b in oxygen-saturated solutions results in heterocycles 3a, 3b, aldehydes 4a, 4b and nitriles 5a, 5b. Density functional theory calculations place the energy of the first and second excited state of the triplet ketones (T1K and T 2K) in 1a, 1b in close proximity to each other. The triplet transition state for cleaving the CN bond in 1a, 1b to form azido and benzyl radicals 1aB, 1bB is located only 3 kcal mol-1 (1 kcal = 4.184 kJ) above T1K, indicating that azido cleavage is feasible. The calculations place the energy of the triplet azido group (TA) in 1a, 1b ～25 kcal mol-1 below T1K; thus, this process is also easily accessible via energy transfer. Further, the transition state barrier for TA to expel N2 and form triplet nitrenes is less than 1 kcal mol-1 above TA in 1a, 1b. Laser flash photolysis of 1a, 1b reveals the formation of the triplet excited ketones of 1a, 1b, which decay to form benzyl radicals 1aB, 1bB and triplet alkylnitrenes. The triplet ketones and the benzyl radicals are quenched with molecular oxygen at rates close to diffusion, whereas the triplet nitrenes react more slowly with oxygen (～5 × 105 M-1s-1). We conclude that the triplet alkylnitrenes intercept the benzyl radicals to form 2 in argon-saturated solution, whereas the benzyl radicals are trapped to form 4 in oxygen-saturated solution; thus, the triplet nitrenes react with oxygen to form 3. CSIRO 2010.
- Ranaweera, Ranaweera A. A. Upul,Zhao, Yu,Muthukrishnan, Sivaramakrishnan,Keller, Christopher,Gudmundsdottir, Anna D.
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p. 1645 - 1655
(2011/09/14)
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- Hydrogen-bonding-promoted oxidative addition and regioselective arylation of olefins with aryl chlorides
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The first, general, and highly efficient catalytic system that allows a wide range of activated and unactivated aryl chlorides to couple regioselectively with olefins has been developed. The Heck arylation reaction is likely to be controlled by the oxidative addition of ArCl to Pd(0). Hence, an electron-rich diphosphine, 4-MeO-dppp, was introduced to facilitate the catalysis. Solvent choice is critical, however; only sluggish arylation is observed in DMF or DMSO, whereas the reaction proceeds well in ethylene glycol at 0.1-1 mol % catalyst loadings, displaying excellent regioselectivity. Mechanistic evidence supports that the arylation is turnover-limited by the oxidative addition step and, most importantly, that the oxidative addition is accelerated by ethylene glycol, most likely via hydrogen bonding to the chloride at the transition state as shown by DFT calculations. Ethylene glycol thus plays a double role in the arylation, facilitating oxidative addition and promoting the subsequent dissociation of chloride from Pd(II) to give a cationic Pd(II)-olefin species, which is key to the regioselectivity observed.
- Ruan, Jiwu,Iggo, Jonathan A.,Berry, Neil G.,Xiao, Jianliang
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supporting information; experimental part
p. 16689 - 16699
(2011/02/23)
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- Synthesis of functionalised acetophenone
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Nickel catalysed Heck arylation of the electron-rich olefin n-butyl vinyl ether with a wide variety of aryl bromides has been accomplished in the ionic liquid [bmim][BF4], affording an efficient green chemistry synthetic procedure for preparing functionalised acetophenone. The reaction gave a high regioselectivity and high yield without the need for the costely or toxic halide scavengers, leading predominantly to a branch-arylated α-product.
- Sun, Li,Pei, Wen,Shen, Chen
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p. 388 - 389
(2007/10/03)
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- Ionic liquid-promoted, highly regioselective Heck arylation of electron-rich olefins by aryl halides
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Palladium-catalyzed regioselective Heck arylation of the electron-rich olefins, vinyl ethers 1a-d, enamides 1e-g, and allyltrimethylsilane 1h, has been accomplished in imidazolium ionic liquids with a wide range of aryl bromides and iodides instead of the commonly used, but commercially unavailable and expensive, aryl triflates. The reaction proceeded with high efficiency and remarkable regioselectivity without the need for costly or toxic halide scavengers, leading exclusively to substitution by aryl groups of diverse electronic and steric properties at the olefinic carbon α to the heteroatom of 1a-g and β to the heteroatom of 1h. In contrast, the arylation reaction in molecular solvents led to mixtures of regioisomers under similar conditions. Several lines of evidence point to the unique regiocontrol stemming from the ionic environment provided by the ionic liquid that alters the reaction pathway. The chemistry provides a simple, effective method for preparing branched, arylated olefins and contributes to the extension of Heck reaction to a wider range of substrates.
- Mo, Jun,Xu, Lijin,Xiao, Jianliang
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p. 751 - 760
(2007/10/03)
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