DFT study on the ruthenium-catalyzed decarbonylative annulation of an alkyne with a six-membered hydroxychromone via C–H/C–C activation

Abstract

We report a density functional theory study on the ruthenium-catalyzed decarbonylative annulation of an alkyne with a six-membered hydroxychromone via C–H/C–C activation. The plausible catalytic cycles involve O–H deprotonation, C–H activation, alkyne insertion and formal [3 + 2] cycloaddition, oxidative insertion and decarbonylation, reductive annulation and the recovery of the catalyst. The calculations confirmed that there are two C–C bonds to be broken to finish the decarbonylation, and to break the C–C bond, originally a CC double bond in 1a, is the favorable reaction path. Since there is no oxidant added to the reaction system, the O₂ molecules in the air help the separation of product 3a and the recovery of the active catalyst, in which triplet and singlet surface crossing would exist. The steady-state approximation and modified energy span model have been employed to calculate the apparent activation free energy of the catalytic cycle.