relation: https://epub.uni-regensburg.de/56230/ title: Intramolecular Nicholas Reaction Enables the Stereoselective Synthesis of Strained Cyclooctynes creator: Monzón, Diego M. creator: Betancort, Juan Manuel creator: Martín, Tomás creator: Ramírez, Miguel Ángel creator: Martín, Víctor S. creator: Díaz Díaz, David subject: 540 Chemie subject: ddc:540 description: Cyclic products can be obtained through the intramolecular version of the Nicholas reaction, which requires having the nucleophile connected to the alkyne unit. Here, we report the synthesis of 1-oxa-3-cyclooctynes starting from commercially available (1R,3S)-camphoric acid. The strategy is based on the initial preparation of propargylic alcohols, complexation of the triple bond with Co-2(CO)(8), and treatment with BF3 center dot Et2O to induce an intramolecular Nicholas reaction with the free hydroxyl group as nucleophile. Finally, oxidative deprotection of the alkyne afforded the cyclooctynes in good yields. Notably, large-sized R substituents at the chiral center connected to the O atom were oriented in such a way that steric interactions were minimized in the cyclization, allowing the formation of cyclooctynes exclusively with (R) configuration, in good agreement with theoretical predictions. Moreover, preliminary studies demonstrated that these cyclooctynes were reactive in the presence of azides yielding substituted triazoles. publisher: MDPI date: 2021 type: info:eu-repo/semantics/article type: Artikel type: doc-type:article type: NonPeerReviewed identifier: Monzón, Diego M., Betancort, Juan Manuel, Martín, Tomás , Ramírez, Miguel Ángel, Martín, Víctor S. und Díaz Díaz, David (2021) Intramolecular Nicholas Reaction Enables the Stereoselective Synthesis of Strained Cyclooctynes. Molecules 26 (6), S. 1629. relation: http://doi.org/10.3390/molecules26061629 relation: 10.3390/molecules26061629