A Multifunctional Metal–Organic Framework for Oxidative C–O Coupling Involving Direct C–H Activation and Synthesis of Quinolines

Abstract

A robust paddle-wheel Cu(II)-based metal-organic framework (MOF) 1, having dual functionalities, namely, Lewis acid and basic sites, has been explored as a heterogeneous catalyst. This MOF, because of its large void volume (10298 Å, 67.6%), large surface area (1480 m/g), and high thermal stability, encouraged us to see its applicability in two catalytic reactions, namely, oxidative C-O coupling (cross-dehydrogentaive coupling reaction) involving direct C-H activation and Friedländer reaction under solvent free and ambient conditions. This study demonstrates the green aspect of MOFs in coupling reactions because of the simplified recovery, shorter reaction time, minimum waste, and smooth activation of the C-H bond, which is very challenging in synthetic chemistry.

Friedländer, Knoevenagel, and Michael Reactions Employing the Same MOF: Synthesis, Structure, and Heterogeneous Catalytic Studies of ([Zn(1,4-NDCA)(3-BPDB)0.5]·(DMF)(MeOH) and [Cd4(1,4-NDCA)4(3-BPDB)4]·2(DMF)

“…When the same reaction was performed in the absence of any catalyst, the yield was found to be only 27%. This indicates that the reaction proceeds catalytically and the observed yields are comparable to those reported earlier in the literature. − …”

“…The Friedländer reaction has been attempted earlier using a number of MOFs (Table ). − From this it is clear that the optimal concentration of the catalyst could be between 1 and 4 mol %. In the present study, we attempted the Friedländer reaction by varying the catalyst concentration between 1 and 4 mol %, and our studies show that the optimal catalyst concentration is 4 mol % for compound I and 2 mol % for compound II .…”

Metal‐Organic Frameworks as Platform for Lewis‐Acid‐Catalyzed Organic Transformations

“…MOFs based on paddle‐wheel secondary building unit are very common in copper‐based frameworks. Sharma et al . has synthesized a robust MOF based on Cu II paddle‐wheel having both Lewis acid as well as basic sites.…”

HKUST-1 Metal Organic Framework as an Efficient Dual-Function Catalyst: Aziridination and One-Pot Ring-Opening Transformation for Formation of β-Aryl Sulfonamides with C–C, C–N, C–S, and C–O Bonds

“…Many reports highlighting the importance for generation of open sites (on activation) in MOF to act as Lewis acid catalyst have been well documented in the literature. 10 In this context, Claisen−Schmidt reaction, 11,12 Knoevenagel condensation, 13−15 epoxidation, 16,17 ring opening of epoxides, 18−21 hydrolysis, 22,23 Friedlander reaction, 24 Friedel−Craft alkylation, 25,26 cyanosilylation, 27−31 acetalization, 32 C−H activation, 33−35 cyclopropanation, 36 Biginelli reactions, 37,38 aldol condensation reaction, 39 Henry reaction, 40,41 carbonyl−ene reaction, 42 Sonogashira reaction, 43 Suzuki coupling, 44 biomass valorization 45,46 cyclization reaction, 47 CO 2 fixation, 48 polymerization, 49 systems, a rational effort in this direction is key for the advancement of this field. The metal-catalyzed nitrene transfer reactions to alkenes affording aziridines, nitrogen analogues of epoxide, are highly valued due to the potential of aziridine to undergo stereo-and regioselective ring-opening transformation forming a wide range of biologically important molecules.…”

“…Many reports highlighting the importance for generation of open sites (on activation) in MOF to act as Lewis acid catalyst have been well documented in the literature . In this context, Claisen–Schmidt reaction, , Knoevenagel condensation, − epoxidation, , ring opening of epoxides, − hydrolysis, , Friedlander reaction, Friedel–Craft alkylation, , cyanosilylation, − acetalization, C–H activation, − cyclopropanation, Biginelli reactions, , aldol condensation reaction, Henry reaction, , carbonyl–ene reaction, Sonogashira reaction, Suzuki coupling, biomass valorization , cyclization reaction, CO 2 fixation, polymerization, and Diels–Alder reaction are a few examples of such reports. However, none of the work emphasizes understanding whether the generation of CUS in the metal sites is crucial in all MOF-catalyzed organic reactions.…”