title: Copper(I)-Catalyzed Cycloaddition of Azides to Multiple Alkynes: A Selectivity Study Using a Calixarene Framework.
abstract: Copper(I)-catalyzed addition of limited amounts of azides to multiple alkynes, which led to statistical mixtures of triazole/acetylene derivatives or, in other cases, resulted in preferred formation of multiple triazoles, was studied at pre-organizable calixarene platforms bearing up to four propargyl groups. Depending on calixarene structures and reaction conditions, the unprecedented specific or selective formation of exhaustively triazolated calixarenes or a complete loss of the selectivity were observed. Both autocatalytic copper activation and a local copper(I) concentration increase due to copper-triazole complexation were thoroughly studied as the most expected reasons for the selectivity and both were disproved. Mixed triazolated/propargylated calixarenes and their copper(I) complexes proved not to be involved in the cascade-like process that was modeled to be driven by an intramolecular transfer of two copper(I) ions from a just-formed binuclear copper intermediate to the adjacent acetylene unit.
authors.affiliation: Department of Chemistry, M. V. Lomonosov Moscow State University, Lenin's Hills 1, 119991 Moscow (Russia).
authors.forename: Alexander
authors.initials: A
authors.lastname: Gorbunov
authors.affiliation: State Research Institute for Chemistry and Technology of Organoelement Compounds, Sh. Entuziastov 38, 105118 Moscow (Russia).
authors.forename: Dmitry
authors.initials: D
authors.lastname: Cheshkov
authors.affiliation: Department of Chemistry, M. V. Lomonosov Moscow State University, Lenin's Hills 1, 119991 Moscow (Russia). kovalev@petrol.chem.msu.ru.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Kovalev
authors.affiliation: Department of Chemistry, M. V. Lomonosov Moscow State University, Lenin's Hills 1, 119991 Moscow (Russia). vatsouro@petrol.chem.msu.ru.
authors.forename: Ivan
authors.initials: I
authors.lastname: Vatsouro
keywords: calixarenes; click chemistry; copper complexes; multiple alkynes; reaction mechanism