Catalytic dehydrogenative borylation of terminal alkynes by POCOP-supported palladium complexes

Pell, Christopher J.; Ozerov, Oleg V.

doi:10.1039/c5qi00074b

Cited by 36 publications

(20 citation statements)

References 32 publications

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“…L3-H , L5-H , L6-H , L8-H , L9-H , L10-H , L11-H , L12-H , L13-H , L14-H , L16-H , L17-H , L18-Ph , and L19-H have been previously reported and were synthesized as described in the literature. L4-H was prepared from 1,3-resorcinol, chlorodicyclohexylphosphine, and triethylamine as a base.…”

Section: Resultsmentioning

confidence: 99%

“…The synthesis of derivatives of organoboronic acids via homogeneous catalysis of C–H bond borylation (Scheme A) is an attractive method of preparation of versatile synthetic building blocks. − The most impressive foundational successes in this chemistry have been associated with catalysis of aromatic C–H borylation by Ir complexes supported by neutral bidentate ligands. − Catalytic borylation of aromatic and other sp 2 and sp 3 C–H bonds has also been realized with a variety of transition-metal and main-group complexes. − Our group has reported on the catalysis of dehydrogenative borylation of the sp C–H bonds in terminal alkynes (DHBTA) using Ir complexes supported by diarylamido-centered SiNN , or PNP − pincer − ligands. Catalysis of DHBTA with other metals has also been reported, − but the activity and the chemoselectivity of the Ir catalysts are superior.…”

Section: Introductionmentioning

confidence: 99%

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Examination of a Series of Ir and Rh PXL Pincer Complexes as (Pre)catalysts for Aromatic C–H Borylation

et al. 2021

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This work follows a previously published study of high-turnover aromatic C–H borylation by Ir complexes supported by POCOP-type ligands incorporating −PiPr2 side donors (L1–L3) using HBpin in the presence of olefins. A variety of pincer-supported Ir and Rh complexes have been tested as precatalysts in the analogous aromatic C–H borylation. The ligands in this study included a number of aryl/bis(phosphine) pincers of the PCP type, as well as PCS, PNP, PNSb, PSiP, and PBP ligands. The syntheses primarily targeted precursors of the (PXL)M(H)(Cl) type (M = Rh, Ir); exceptions included complexes (L15)Ir(H)(OAc), (L17)Ir(COE), (L18)Ir(H)4, and (L16)Rh(H2). The catalytic competence was tested using C6D6 as the substrate (and solvent) with HBpin and 1-hexene as reagents. C–H borylation and hydroboration of 1-hexene were the two competing catalytic reactions. None of the Rh complexes tested displayed any C–H borylation activity. Among the Ir complexes, only those possessing a central aryl site in the pincer showed significant C–H borylation activity with C6D6. The most promising precatalysts (L3)Ir(H)(Cl), (L4)Ir(H)(Cl), (L7)Ir(H)(Cl), (L11)Ir(H)(Cl), (L13)Ir(H)(Cl), and (L15)Ir(H)(OAc) were tested in the C–H borylation of C6H5F and C6H5CF3. All of these catalysts showed a roughly statistical preference for the borylation of only meta and para sites in C6H5CF3. For C6H5F borylation of all three sites (ortho, meta, para) was observed. Catalysts supported by the ligands L3 and L11 showed the highest rate of reaction and higher selectivity for C–H borylation vs hydroboration. Borylation of m-ClC6H4Me catalyzed by (L3)Ir(H)(Cl) and (L11)Ir(H)(Cl) resulted in only the borylation of only one aromatic C–H site (meta to both substituents), <10% of borylation of the benzylic site, and no borylation of the C–Cl moiety.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Examination of a Series of Ir and Rh PXL Pincer Complexes as (Pre)catalysts for Aromatic C–H Borylation

et al. 2021

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“…The POCOP‐supported palladium complexes could also catalyzed the cross‐dehydrogenative borylation of terminal alkynes with H−Bpin . Compared with the previous (SiNN)Ir complexes, the palladium catalyst enabled the spC−B bond‐forming reaction in one pot with an equivalent loading of alkynes and H−Bpin; however, a long reaction time (several days) and high catalyst loading (5 mol %) were required, and side reactions such as hydrogenation and a limited substrate scope of alkynes were also suffered.…”

Section: Formation Of Spc−heteroatom Bondsmentioning

confidence: 99%

Cross‐Dehydrogenative Alkynylation: A Powerful Tool for the Synthesis of Internal Alkynes

et al. 2020

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“…Calcd for C 41 H 66 BO 3 P 2 Rh: C, 62.92; H, 8.50. Found: C,63.39;H,8. Isomerization of 6 to Rh{η 3 -CH 2 CHCHCH(Bpin)Pr}{κ 2 -P,P-[xant(P i Pr 2 ) 2 ]} (7). A Schlenk flask provided with a Teflon closure was filled with a solution of 6 (100 mg, 0.13 mmol) in pentane (5 mL) and heated in an oil bath (50 °C) for 24 h. After this, the resulting solution was checked by 31 P{ 1 H} NMR spectroscopy, showing quantitative conversion to complex 7.…”

Section: ■ Concluding Remarksmentioning

confidence: 99%

Rhodium-Mediated Dehydrogenative Borylation–Hydroborylation of Bis(alkyl)alkynes: Intermediates and Mechanism

et al. 2019

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Complex Rh(Bpin){κ 3 -P,O,P-[xant(P i Pr 2 ) 2 ]} (Bpin = pinacolboryl; xant(P i Pr 2 ) 2 = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene) catalyzes the addition of B 2 pin 2 to 3-hexyne and 4octyne to give equimolecular mixtures of conjugated boryldienes and borylolefins, as a result of the addition of the B−B bond of the diborane to different molecules of alkynes and hydride transfer from one to the other. Both the dehydrogenative borylation and hydroborylation reactions form a catalytic cycle that has been deduced on the basis of stoichiometric studies. Complex Rh(Bpin){κ 3 -P,O,P-[xant(P i Pr 2 ) 2 ]} promotes the dehydrogenative borylation of alkynes by means of reactions of insertion of the alkyne into the Rh−B bond, Z−E isomerization of the β-borylalkenyl ligand of the resulting Rh−alkenyl species, and C γ −H bond activation of the alkyl substituent attached to the alkenyl C α atom. As a consequence of the formation of boryldienes, the monohydride RhH{κ 3 -P,O,P-[xant(P i Pr 2 ) 2 ]} is generated. The latter in a sequential manner reacts with the alkynes and the diborane to give the borylolefin hydroborylation products, via Rh−alkenyl intermediates, and regenerates the initial Rh−boryl compound. The latter also promotes stoichiometric cycles to prepare diboryl-2-olefins via allyl intermediates. In addition, the stoichiometric rhodiummediated formation of 1-boryl-2-olefins is shown.

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Catalytic dehydrogenative borylation of terminal alkynes by POCOP-supported palladium complexes

Cited by 36 publications

References 32 publications

Examination of a Series of Ir and Rh PXL Pincer Complexes as (Pre)catalysts for Aromatic C–H Borylation

Examination of a Series of Ir and Rh PXL Pincer Complexes as (Pre)catalysts for Aromatic C–H Borylation

Cross‐Dehydrogenative Alkynylation: A Powerful Tool for the Synthesis of Internal Alkynes

Rhodium-Mediated Dehydrogenative Borylation–Hydroborylation of Bis(alkyl)alkynes: Intermediates and Mechanism

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