ChemInform Abstract: Palladium(II)‐Catalyzed Cyclizative Cross‐Coupling of ortho‐Alkynylanilines with ortho‐Alkynylbenzamides under Aerobic Conditions

Yao, Bo; Wang, Qian

doi:10.1002/chin.201422123

Cited by 1 publication

(1 citation statement)

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“…One representative example of palladium-catalyzed heterocyclization−coupling is provided by the reactions of 2alkynylbenzamides. These substrates have been shown to undergo palladium-catalyzed O-cyclization−coupling reactions with aryl 27 and allyl 28 halides, alkenes, 29−33 carbon monoxide, 34 and 2-alkynyldimethylanilines, 35 as well as oxidative homocoupling, 36 in all cases with good control of the regiochemistry (exo/endo) of cyclization (Scheme 2).…”

Section: ■ Introductionmentioning

confidence: 99%

Regioselective Palladium-Catalyzed Heterocyclization–Sonogashira Coupling Cascades from 2-Alkynylbenzamides and Terminal Alkynes: Experimental and DFT Studies

et al. 2018

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A regioselective heterocyclization–Sonogashira coupling cascade between 2-alkynylbenzamides and terminal alkynes is described. The reaction proceeds under Pd(II) catalysis, with air used as a terminal oxidant to regenerate the catalyst from the Pd(0) produced in the C–C coupling. The cascade process provides alkynyl-substituted isobenzofuranimine products in a single operation. These products are the result of a 5-exo O-cyclization, while products derived from the alternative 6-endo cyclization mode are observed in minor amounts. Two competing mechanisms have been considered to account for the observed results. Both involve heterocyclization, alkyne C–H activation, and reductive elimination steps but differ in the relative order of the first two. Control experiments using a preformed alkynylpalladium complex have shown that a mechanism starting with alkyne C–H activation is viable. On the other hand, DFT calculations indicate that the alternative cyclization-first mechanism is also competitive, particularly when PPh3 is used as ligand. Calculations also suggest that the exo cyclization is favored over the endo mode by the presence of PPh3 and σ-C Pd ligands in the activated complex undergoing cyclization.

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