Catalytic cyclization of 2-alkyl-1-ethynylbenzene derivatives was implemented by TpRuPPh3(CH3CN)2PF6 (10 mol %) in hot toluene (105 degrees C, 36-100 h) to form 1-substituted-1H-indene and 1-indanone products; such cyclizations proceeded more efficiently for substrates bearing electron-rich benzenes. We propose that the cyclization mechanism involves a 1,5-hydrogen shift of initial metal-vinylidene intermediate.

Ruthenium-catalyzed cyclization of 2-alkyl-1-ethynylbenzenes leads to 1-substituted-1H-indene and 1-indanone products, with more efficient synthesis for electron-rich benzene substrates.

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Ruthenium-catalyzed cyclization of 2-alkyl-1-ethynylbenzenes via a 1,5-hydrogen shift of ruthenium-vinylidene intermediates.

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