Mechanistic study in azide-alkyne cycloaddition (CuAAC) catalyzed by bifunctional trinuclear copper(I) pyrazolate complex: Shift in rate-determining step

Mechanistic study in azide-alkyne cycloaddition (CuAAC) catalyzed by bifunctional trinuclear copper(I) pyrazolate complex: Shift in rate-determining step Full article

Journal

Journal of Catalysis
ISSN: 0021-9517 , E-ISSN: 1090-2694

Output data

Year: 2020, Volume: 390, Pages: 37-45 Pages count : 9 DOI: 10.1016/j.jcat.2020.07.010

Authors

Larionov Vladimir A. ^1,2 , Stashneva Anna R. ^1,3 , Titov Aleksei A. ¹ , Lisov Alexey A. ^4,5 , Medvedev Michael G. ^4,5 , Smol'yakov Alexander F. ^1,6 , Tsedilin Andrey M. ⁵ , Shubina Elena S. ¹ , Maleev Victor I. ¹

Affiliations

1	A. N. Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Sciences, Vavilov Str. 28, 119991 Moscow, Russian Federation
2	Department of Inorganic Chemistry, Peoples’ Friendship University of Russia (RUDN University), Miklukho-Maklaya Str. 6, 117198 Moscow, Russian Federation
3	Dmitry Mendeleev University of Chemical Technology of Russia, Miusskaya sq. 9, 125047 Moscow, Russian Federation
4	Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1/3, 119991 Moscow, Russian Federation
5	N. D. Zelinsky Institute of Organic Chemistry of Russian Academy of Sciences, Leninsky prospect 47, 119991 Moscow, Russian Federation
6	Plekhanov Russian University of Economics, Stremyanny per. 36, 117997 Moscow, Russian Federation

Trinuclear copper(I) pyrazolate [Cu(3,5-(CF3)2Pz)]3 was employed in a mechanistic study of azide-alkyne cycloaddition (CuAAC). It was shown that the copper complex operates as a bifunctional catalytic system (copper source and Brønsted base) under mild conditions (RT and air atmosphere) at low catalyst loading (1 mol%). The rate-determining step of the reaction is the first C-N bond formation between azide and acetylene (azide migratory insertion) but not the copper(I) acetylide formation as commonly assumed. It was supported by the observed kinetic isotope effect equaling 1.1 and by DFT calculations. The reaction has a second-order dependence on the catalyst concentration implicating the two copper(I) centers participate in the metallacycle formation step from “bis-butterfly” tetranuclear complex Cu4L4(RC≡CH)2 in the rate-determining step. DFT calculations proved that the pyrazolate ligand acts as a Brønsted base and deprotonates the acetylene molecule providing successful catalysis. A plausible catalytic cycle of the reaction has constructed based on DFT calculations.

Larionov V.A. , Stashneva A.R. , Titov A.A. , Lisov A.A. , Medvedev M.G. , Smol'yakov A.F. , Tsedilin A.M. , Shubina E.S. , Maleev V.I.
Mechanistic study in azide-alkyne cycloaddition (CuAAC) catalyzed by bifunctional trinuclear copper(I) pyrazolate complex: Shift in rate-determining step
Journal of Catalysis. 2020. V.390. P.37-45. DOI: 10.1016/j.jcat.2020.07.010 WOS Scopus OpenAlex

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