Rh-catalyzed (4+1) carbocyclization of chalcones with internal alkynes: A DFT study

Abstract

Computational studies were performed to provide mechanistic insights into the (4+1) carbocyclization mechanism from chalcones with internal alkynes catalyzed by rhodium catalysis. Computational results suggested that cationic rhodium (C_p^tRhOAc⁺) was generally used as the active catalyst, and the generation of 2H-furanium salt can be divided into three stages: formation of pyrylium salt, hydrolysis, and 2H-furanium salt formation. The factors responsible for the regio-, chem- and stereo-selectivities are discussed. The regio- and chem-selectivity step is identified as the migratory insertion process in the first catalytic cycle. The reason can be understood from the electronic effect. The stereochemistry-determining-step is the migratory insertion process in the second catalytic cycle, which can be ascribed to the steric effect as RSS-TS_21–22 identifies a more expansive structure.