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Computational Investigation of the 1,4‐Rh Shift in the [(Ph 2 PCH 2 CH 2 PPh 2 )Rh]‐Catalyzed Alkyne Arylation Reaction
Author(s) -
Kantchev Eric Assen B.,
Zhou Feng,
Pangestu Surya R.,
Sullivan Michael B.,
Su Haibin
Publication year - 2015
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201501098
Subject(s) - chemistry , catalysis , hydrolysis , steric effects , reductive elimination , medicinal chemistry , alkyne , phenylboronic acid , transmetalation , substrate (aquarium) , hydride , catalytic cycle , density functional theory , oxidative addition , stereochemistry , computational chemistry , organic chemistry , metal , oceanography , geology
Computations (density functional theory) of the post‐transmetallation stages (carborhodation, 1,4‐shift consisting of C–H oxidative addition/C–H reductive elimination, and hydrolysis) in the catalytic cycle for the arylation of 2‐butyne with phenylboronic acid mediated by [(dppe)Rh I ] catalyst [dppe = 1,2‐bis(diphenylphosphanyl)ethane] shows that (1) carborhodation is facile (Δ G ‡ ≈ 10 kcal mol –1 ); (2) the barriers of the 1,4‐shift and hydrolysis are approximately equal (Δ G ‡ ≈ 19–24 kcal mol –1 ); (3) the 1,4‐Rh shift product is ca. 5 kcal mol –1 more stable than the non‐rearranged product, in good agreement with the experimental results. Analogous computations for ( Z )‐2‐butene as a model substrate show that (1) carborhodation is much slower (Δ G ‡ ≈ 19 kcal mol –1 ); (2) the sp 3 → sp 2 1,4‐shift is faster than the sp 2 → sp 2 1,4‐shift; (3) the hydrolysis of Rh–C σ bonds depends more on the steric environment than the hybridization of the C atom; and (4) β‐hydride elimination is the most likely reaction after carborhodation.