5006-39-3Relevant articles and documents
Discovery and mechanistic investigation of Pt-catalyzed oxidative homocoupling of benzene with PhI(OAc)2
Abu-Omar, Mahdi M.,Nabavizadeh, S. Masoud,Niroomand Hosseini, Fatemeh,Park, Chan,Wu, Guang
supporting information, p. 2477 - 2486 (2020/03/05)
We present a Pt-catalyzed direct coupling of benzene to biphenyl. This catalytic reaction employs a cyclometalated platinum(ii) complex [PtMe(bhq)(SMe2)] (bhq = benzo[h]quinolate) with PhI(OAc)2 as an oxidant and does not require an acid, a co-catalyst or a solvent. The reaction kinetics and characterization of potential catalytic species are reported. The reaction is first-order in Pt and second-order in benzene, which implicates the second C-H activation step as rate-determining. A Pt(ii)/Pt(iv) catalytic cycle is suggested. The reaction commences by oxidation of the Pt(ii) complex to give the platinum(iv) species [Pt(bhq)(SMe2)(OAc)2](OAc) followed by C-H activation of benzene to afford the intermediate [PtPh(bhq)(SMe2)(OAc)](OAc) concurrently with the release of HOAc. A second benzene molecule reacts similarly to give the diphenyl intermediate [PtPh2(bhq)(SMe2)](OAc). C-C bond forming reductive elimination ensues to regenerate Pt(ii) and complete the catalytic cycle. The proposed mechanism has been examined by DFT computations, which provide support to experimental findings.
Palladium-Catalyzed Cross-Dehydrogenative Coupling of o-Xylene: Evidence of a New Rate-Limiting Step in the Search for Industrially Relevant Conditions
álvarez-Casao, Yolanda,van Slagmaat, Christian A. M. R.,Verzijl, Gerard K. M.,Lefort, Laurent,Alsters, Paul L.,Fernández-Ibá?ez, M. ángeles
, p. 2620 - 2626 (2018/05/04)
An efficient cross-dehydrogenative coupling of o-xylene under neat conditions, which brings important industrial benefits towards the synthesis of a monomer used in polyimide resins, is reported. The catalyst based on the combination of Pd/N ligand/carboxylate=1:1:2 does not require a Cu cocatalyst and proceeds at 11 bar of O2 pressure. Evaluation of the deuterium kinetic isotope effect (KIE) provides evidence for three different rate-determining steps, which depend on the reaction conditions (medium, temperature). Under the reported neat conditions, the dissociation of a carboxylate-bridged dimer to generate a more reactive monometallic Pd species is proposed to be the rate-limiting step.
A method for preparing four methyl biphenyl
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Paragraph 0079; 0080, (2017/01/26)
The invention provides a preparation method of tetramethyl biphenyl, which comprises the following steps: mixing halogenated o-xylene, magnesium metal, iodine, ether and transition metal catalyst, and reacting to obtain the tetramethyl biphenyl, wherein the mol ratio of ether to magnesium metal is (0.5-3):1. Compared with the prior art of synthesizing tetramethyl biphenyl from halogenated o-xylene, the invention has the following advantages: by using the raw material halogenated o-xylene as the solvent, the preparation of the format reagent and the coupling reaction are carried out in the initial raw material, so that the addition of abundant anhydrous solvent as the reaction medium is not needed, thereby lowering the reaction cost and simplifying the production technique; the magnesium metal is directly added into the halogenated o-xylene to obtain the format reagent, so the process is simple and the conditions are mild and controllable; and the raw material, the concentration of which in the reaction system is high, is used as the solvent and participates in the oxidation-reduction process in the coupling reaction, no oxidizer is needed, so the reaction conditions are mild and controllable.