A high hydroarylation activity of K2PtCl4/AgOTf catalyst in the reaction of propiolic acid with unactivated and activated arenes

Oyamada, Juzo; Hashimoto, Takuya; Kitamura, Tsugio

doi:10.1016/j.jorganchem.2009.07.008

Cited by 12 publications

(3 citation statements)

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“…The stoichiometric proton dissociated from intermediate B alone is not sufficient enough to cleave the Pt–C σ bond in the alkenyl complex C (Scheme ). This observation is quite consistent with previously reported experimental findings for all palladium(II)- and platinum(II)-catalyzed hydroarylation reactions where a Brønsted acid (typically CF 3 COOH) is required as a cocatalyst. − Labeling studies with d 1 -TFA showed the incorporation of deuterium in the product, indicating that the acid is actually consumed for the protolytic cleavage. , …”

Section: Resultssupporting

confidence: 91%

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Mechanistic Studies on Platinum(II) Catalyzed Hydroarylation of Alkynes

et al. 2014

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The dicationic acetylene platinum(II) complex [ P t ( P N P ) ( C 2 H 2 ) ] ( B F 4 ) 2 (PNP = 2,6-bis-(diphenylphosphinomethyl)pyridine) was generated in situ by ligand substitution from the ethylene complex [Pt(PNP)-(C 2 H 4 )](BF 4 ) 2 and was reacted with a series of arenes at low temperature. Only electron-rich arenes added across the coordinated C−C triple bond and gave the corresponding arylalkenyl complexes (E)-[Pt(PNP)(CHCHAr)]BF 4 (Ar = C 6 Me 5 , C 6 H 2 Me 3 -2,4,6, C 6 H 3 Me 2 -2,6, C 6 H 3 Me 2 -2,4). A slow E− Z isomerization of the arylalkenyl complexes was observed. Single-crystal X-ray structure analyses were obtained for both E and Z isomers of the pentamethylbenzene derivative. The E isomers of [Pt(PNP)(CHCHAr)]BF 4 (Ar = C 6 Me 5 , C 6 H 2 Me 3 -2,4,6) reacted with excess HBF 4 •Et 2 O to give the corresponding arylalkene complexes [Pt(PNP)(CH 2 CHAr)](BF 4 ) 2 , whereas the Z isomers did not undergo immediate protonolysis. Using (E)-[Pt(PNP)(CDCDC 6 Me 5 )]BF 4 it was shown that the stereochemistry of the C−C double bond in the protonolysis product depends on the nature of the acid anion HX (X − = Cl − , BF 4 − ). The catalytic hydroarylation was studied in solution by NMR spectroscopy. The reaction studies provide a more refined view of the individual steps proposed for the Friedel−Crafts type mechanism of the Pt II -catalyzed intermolecular hydroarylation of alkynes.

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Section: Resultssupporting

confidence: 91%

“…Modifications of the platinum(II) catalyst, i.e. using PtCl 2 /2AgOTf and K 2 PtCl 4 /AgOTf, led to an enhanced catalytic activity. The K 2 PtCl 4 /AgOTf system proved to be an efficient catalyst for a broader range of aromatic and heteroaromatic compounds, including benzene, pyrroles, thiophenes, and polystyrene…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Studies on Platinum(II) Catalyzed Hydroarylation of Alkynes

et al. 2014

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“…The alkenylation of arenes with alkynes is one of the most straightforward strategies to build versatile structural motifs of polysubstituted olefins . A number of transition-metal catalysts have been reported to promote the alkenylation of (hetero)arenes with alkynes. − In addition, the Friedel–Crafts reaction of arenes with in situ generated vinyl carbocations I-a (Scheme , A), which is generally difficult to achieve and requires in combined acids (e.g., HF-SbF 5 , TfOH-SbF 5 ) as dual super acids and solvents, has appeared as a complementary yet appealing strategy for alkenylation reaction. , Kitamura found that stoichiometric amounts of CF 3 CO 2 H could promote the hydroarylation reaction of phenylacetylene with toluene via carbocations I-b , but with lower regioselectivity . Recently, Nelson has developed weakly coordinating anions (WCA) salts and thioureas catalysis for the functionalization of unactivated C–H bonds via vinyl carbocations II (Scheme , B) …”

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confidence: 99%