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

Abstract

(Chemical Equation Presented) Catalytic cyclization of 2-alkyl-1- ethynylbenzene derivatives was implemented by TpRuPPh3(CH 3CN)2PF6 (10 mol %) in hot toluene (105 °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. © 2007 American Chemical Society.