Реферат: A selective dimerization of 2-cyclopenten-1-one, which proceeds through the [2+2]-cycloaddition mechanism, was successfully carried out under soft UV irradiation with a reagent trapped within the pores of the metal-organic framework. Such approach allowed achieving very high (up to 98%) selectivity of the formation of its head-to-tail anti- dimer among other possible diastereomeric dimers, while similar selectivity rarely exceeds 60% using other known approaches. The used metal-organic framework [Eu2(DMF)4(ttdc)3] (DMF = N,N-dimethylformamide; H2ttdc – transthienothiophene-2,5-dicarboxylic acid), containing regular nano-sized pores, acted as a matrix - a “reaction vessel” - which adsorbed the reagent molecules. A highly ordered arrangement of 2-cyclopenten-1-one molecules in the MOF pores, provided by host-guest hydrogen bonds, predetermines the geometry of its dimer at the molecular level and subsequently extremely high selectivity of its formation, confirmed by 1H NMR spectroscopy. The stability and geometric rigidity of the porous coordination network structure excludes the formation of other possible product isomers in the reaction. A crystal structure for the inclusion compound of target product with MOF was determined by single crystal X-ray diffraction analysis, providing an unambiguous confirmation for the reaction passing distinctively within the voids of the coordination framework and additional insights into the reaction selectivity in terms of host-guest interactions. Similar results were obtained for 2-methyl-2-cyclopenten-1one, while for 3-methylated derivative its diastereoselective [2+2] dimerization was found to be impeded due to the different guest orientation in the MOF pores, not providing a specific product-like pre-organization of the reagent molecules.

Библиографическая ссылка: Demakov P.A. , Fedin V.P.
Diastereoselective [2+2]-photodimerization of 2-cyclopenten-1-one within a metal-organic framework
9th Asian Conference on Coordination Chemistry 19-22 Feb 2024