Capturing the Organic Species Derived from the C–C Cleavage and in Situ Oxidation of 1,2,3,4-Tetra(pyridin-4-yl)cyclobutane by [CuCN]_n-Based MOFs

Abstract

The solvothermal cycloreversion and in situ oxidation of 1,2,3,4-tetra(pyridin-4-yl)cyclobutane (tpcb) within [CuCN] -based MOFs were investigated. The radical mechanism for the cycloreversion of tpcb ligands was supported by capturing a 1,3-butadiene species 1,2,3,4-tetra(4-pyridyl)-1,3-butadiene (tpyb) into {[Cu(μ-CN)(tpcb)(tpyb)]·HO} in the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO). Without TEMPO, a furan-based ligand 2,3,4,5-tetra(4-pyridyl)furan (tpyf) was generated within {[Cu(μ-CN)(tpyf)]·4MeCN} via the C-C cleavage, followed by in situ oxidation in acidic condition.

Thermal Elimination of Ethylene from Cyclobutyl Groups Characterized by X‐ray Crystallography in a Metal–Organic Framework Matrix

“… Schematic illustrations of a) the formation of ethylene and cyclobutane via the decarbonylation of cyclopentanone, b) the formation of two alkene species through decomposition of a cyclobutane derivative, c) the conversion of a cyclobutyl ring into a furan derivative via oxidation of a biradical intermediate and d) the thermolytic expulsion of ethylene from cyclobutyl rings on the cbtt ligand in MUF‐88.…”

“…Although, there are many reports on cyclobutyl ring formation via cycloaddition reactions in MOFs, only a small number of studies have focused on the reverse reaction . Cyclobutyl groups in framework materials can also be converted into furan derivatives via thermal cleavage followed by oxidation of the resulting biradical intermediate . These examples, however, do not generate free vinyl groups and are therefore of limited use for further synthetic transformations.…”

Elimination of Ethylene from Cyclobutyl Groups Characterised by X-ray Crystallography in a Metal-Organic Framework Matrix

“…[34] The existence of biradical intermediates has been exploited for synthesis (Figure 8c). [27] Based on this, we propse the pathway shown in Figure 8d. While we did not attempt to observe the putative radical intermediate, we were able to confirm the identities of the two final products.…”

“…Figure 8. Schematic illustrations of a) formation of ethylene and cyclobutane through decarbonylation of cyclopentanone, [33] b) formation of two alkene species through decomposition of a cyclobutane derivative, [34] c) conversion of a cyclobutane ring into a furan derivative via oxidation of a biradical intermediate [27] and d) decomposition of cyclobutyl groups on the cbtt ligand in MUF-88.…”

“…[26] Cyclobutyl groups in framework materials can also be converted into furan derivatives via thermal cleavage followed by oxidation of the resulting biradical intermediate. [27] These examples, however, do not generate free vinyl groups and are therefore of limited use for further synthetic transformations.…”