DFT Study on the Addition Reaction Mechanism of Phenylacetylene and NHC–Borane Catalyzed by DTBP

The mechanism of the electrophilic addition between phenylacetylene and N-heterocyclic carbene borane (NHC–borane), initiated by di-tert-butyl peroxide (DTBP), was elucidated at the M06-2X-D3/ma-def2-TZVP level to yield the Z-configured product. The computational results show that DTBP undergoes homolysis to generate two t-BuO· radicals; subsequently, it undergoes an H-shift reaction with N-heterocyclic carbene borane to form the N-heterocyclic carbene boron radical. Then, it is added to phenylacetylene to obtain the product radical intermediate. Finally, the product is yielded via an H-shift reaction. Meanwhile, this paper also explores the formation pathways of relevant byproducts. Structural analysis of the reaction reveals that weak interactions have a significant impact on the selectivity of the Z-configuration of the product. In addition, electron spin density contour maps are used to explain the electron distribution and reaction sites during the reaction process. This paper will provide relevant theoretical support for this type of addition reaction.