Arylation/Intramolecular Conjugate Addition of 1,6-Enynes Enabled by Manganese(I)-Catalyzed C-H Bond Activation.

An arylation/intramolecular conjugate addition of cyclohexadienone-containing 1,6-enynes has been established through initiation by manganese(I)-catalyzed C-H bond activation. This tandem reaction involved unusual E/ Z-isomerized alkenyl-Mn intermediates and proceeded smoothly with high chemoselectivities and perfect atom economy. The cyclization products could be further transformed to various structures. Mechanistic studies suggested that cleavage of the C-H bond was involved in the turnover-limiting step, and a manganese carbene anion intermediate was proposed to explain such an E/ Z isomerization process.