N‐Heterocyclic Carbene Copper(I) Rotaxanes Mediate Sequential Click Ligations with All Reagents Premixed

• Published in: Angewandte Chemie International Edition Vol. 59; no. 28; pp. 11278 - 11282
• Main Authors: Hsueh, Fang‐Che, Tsai, Chi‐You, Lai, Chien‐Chen, Liu, Yi‐Hung, Peng, Shie‐Ming, Chiu, Sheng‐Hsien
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 06.07.2020; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: Alkynes; Azide; carbenes; catalysis; Catalysts; Chemistry; Chemistry, Multidisciplinary; Copper; Coupling; cycloaddition; host–guest systems; Irradiation; Physical Sciences; Radiation; Reagents; Rotaxanes; Science & Technology; Triazoles; 1,3-DIPOLAR CYCLOADDITIONS; cycloaddition; host-guest systems; AZIDES; rotaxanes; POLYMER; carbenes; CHEMISTRY; REACTIVITY; catalysis; ALKYNES
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202001398

We have prepared NHC‐CuI complexes with a rotaxane structure and used them as sterically sensitive catalysts for one‐pot sequential copper‐catalyzed azide/alkyne cycloadditions in solutions containing all of the coupling partners premixed in unprotected form. Most notably, a photolabile and sterically encumbered complex first catalyzed the coupling of a less bulky azide/alkyne pair; after removing the protective macrocyclic component from the rotaxane structure, through irradiation with light, the exposed dumbbell‐shaped NHC‐CuI complex catalyzed the second click reaction of a bulkier azide/alkyne pair. Using this approach, we obtained predominantly, from a single sealed pot, a bis‐triazole product (84 %) from a mixture of two sterically distinct azides and a diyne. Sequential click ligations occur efficiently in a sealed flask containing all coupling partners (azides, alkynes) in their unprotected forms and a photolabile interlocked N‐heterocyclic carbene‐CuI catalyst.