01018nas a2200181 4500008004100000022001400041245011300055210006900168260011000237300001600347490000700363520025300370100002400623700001800647700002400665700002000689856012700709 2014 eng d a1477-922600aDesign and development of POCN-pincer palladium catalysts for C-H bond arylation of azoles with aryl iodides0 aDesign and development of POCNpincer palladium catalysts for CH  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcNOV a16084-160960 v433 a

{Well-defined and efficient POCN-ligated palladium complexes have been developed for the direct C H bond arylation of azoles with aryl iodides. The phosphinite-amine pincer ligands 1-(R2PO)-C6H4-3-((CH2NPr2)-Pr-i) 1R2POCNIPr2-H; R = `Pr (1a)

1 aKhake, Shrikant, M.1 aSoni, Vineeta1 aGonnade, Rajesh, G.1 aPunji, Benudhar uhttps://library.ncl.res.in/content/design-and-development-pocn-pincer-palladium-catalysts-c-h-bond-arylation-azoles-aryl-000966nas a2200181 4500008004100000022001400041245016300055210006900218260011000287300001600397490000600413520014400419100002200563700002400585700002400609700002000633856013100653 2015 eng d a2046-206900aMono- and binuclear palladacycles via regioselective C-H bond activation: syntheses, mechanistic insights and catalytic activity in direct arylation of azoles0 aMono and binuclear palladacycles via regioselective CH bond acti aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcSEP a81502-815140 v53 a

{Regioselective C-H bond palladation of the hybrid pincer-type ligands, 3-R2PO-C6H4-1-(CH2NPr2)-Pr-i [(POCNiPr2)-P-R2-H; R = Ph (1a)

1 aPandey, Dilip, K.1 aKhake, Shrikant, M.1 aGonnade, Rajesh, G.1 aPunji, Benudhar uhttps://library.ncl.res.in/content/mono-and-binuclear-palladacycles-regioselective-c-h-bond-activation-syntheses-mechanistic-002017nas a2200193 4500008004100000245014400041210006900185260000800254300001400262490000700276520128500283100002401568700002201592700002301614700002401637700001701661700002001678856012501698 2016 eng d00aMechanistic insights into pincer-ligated palladium-catalyzed arylation of azoles with aryl Iodides: evidence of a Pd-II-Pd-IV-Pd-II pathway0 aMechanistic insights into pincerligated palladiumcatalyzed aryla cMAR a875–8860 v353 a

Pincer-based (R2POCNR′2)PdCl complexes along with CuI cocatalyst catalyze the arylation of azoles with aryl iodides to give the 2-arylated azole products. Herein, we report an extensive mechanistic investigation for the direct arylation of azoles involving a well-defined and highly efficient (iPr2POCNEt2)PdCl (2a) catalyst, which emphasizes a rare PdII–PdIV–PdII redox catalytic pathway. Kinetic studies and deuterium labeling experiments indicate that the C–H bond cleavage on azoles occurs via two distinct routes in a reversible manner. Controlled reactivity of the catalyst 2a underlines the iodo derivative (iPr2POCNEt2)PdI (3a) to be the resting state of the catalyst. The intermediate species (iPr2POCNEt2)Pd-benzothiazolyl (4a) has been isolated and structurally characterized. A determination of reaction rates of compound 4a with electronically different aryl iodides has revealed the kinetic significance of the oxidative addition of the C(sp2)–X electrophile, aryl iodide, to complex 4a. Furthermore, the reactivity behavior of 4a suggests that the arylation of benzothiazole proceeds via an oxidative addition/reductive elimination pathway involving a (iPr2POCNEt2)PdIV(benzothiazolyl)(Ar)I species, which is strongly supported by DFT calculations.

1 aKhake, Shrikant, M.1 aJagtap, Rahul, A.1 aDangat, Yuvraj, B.1 aGonnade, Rajesh, G.1 aVanka, Kumar1 aPunji, Benudhar uhttps://library.ncl.res.in/content/mechanistic-insights-pincer-ligated-palladium-catalyzed-arylation-azoles-aryl-iodides02240nas a2200205 4500008004100000022001400041245009000055210006900145260000800214300001400222490000700236520155700243100002401800700001801824700002101842700002401863700001701887700002001904856011001924 2018 eng d a0276-733300aMechanism of nickel(II)-catalyzed C(2)-H alkynylation of indoles with alkynyl bromide0 aMechanism of nickelIIcatalyzed C2H alkynylation of indoles with  cJUL a2037-20450 v373 a

The nickel system (THF)(2)NiBr2/phen has recently been shown as an efficient catalyst for the C-H bond alkynylation of diverse heteroarenes with (triisopropylsilyl)alkynyl bromide via monodentate chelation assistance. Herein, we report an extensive mechanistic investigation for the direct alkynylation of indoles involving the well-defined nickel catalyst, which features a coordinative insertion pathway of alkynyl bromide with the Ni(II) catalyst. Catalytic relevant nickel complexes, (phen)NiCl2 (5), (phen)(2)NiCl2 (6) and [(phen)(3)Ni].NiCl4 (7) were isolated, and the complexes 6 and 7 were structurally characterized. Well-defined complexes were as competent as the in situ generated catalyst system (THF)(2)NiBr2/phen for the alkynylation of indoles. Various controlled studies and reactivity experiments were performed to understand the probable pathway for the alkynylation reaction. Kinetics analysis highlights that the complex (phen)NiX2 acts as a precatalyst, and the involvement of substrate indole and LiO'Bu are essential for the generation of the active catalyst. Deuterium labeling and kinetic studies suggest that the process involving C-H cleavage and carbo-nickelation of indole is a crucial rate influencing step. Reactivity study of various alkynyl compounds with nickel-species highlights a migratory insertion route for the reaction. DFT calculations firmly support the experimental findings and suggest the coordinative insertion pathway of alkynyl bromide rather than oxidative addition toward the nickel(II) center.

1 aKhake, Shrikant, M.1 aJain, Shailja1 aPatel, Ulhas, N.1 aGonnade, Rajesh, G.1 aVanka, Kumar1 aPunji, Benudhar uhttps://library.ncl.res.in/content/mechanism-nickelii-catalyzed-c2-h-alkynylation-indoles-alkynyl-bromide