Visible Light Mediated Heck Coupling of Inactivated Aryl Fluoride/Chloride Over a Sulfonic Acid Functionalized, Melamine‐based Metal‐free Porphyrin Photocatalyst

Abstract

We report the synthesis of a new, sulfonic acid functionalized, melamine‐based metal‐free porphyrin photocatalyst (MBMFPc) for the C−C coupling of the most unreactive aryl halides with alkenes under visible light irradiation. The ionic liquid‐based photocatalyst was characterized using various analytical techniques Proton Nuclear Magnetic Resonance (1HNMR) Spectroscopy, Carbon Nuclear Magnetic Resonance (13CNMR) Spectroscopy, Fourier Transformed Infrared Spectroscopy (FT‐IR), Energy‐dispersive X‐ray Spectroscopy (EDAX), Scanning Electron Microscope (SEM), Brunauer‐Emmett‐Teller (B.E.T) and Ultraviolet‐Visible Spectroscopy (UV‐Vis). The MBMFPc photocatalyst with noticeable Hammett acidity (0.56) and optimal bandgap of 1.44 eV was found to as an effective catalyst in the Mizoroki‐Heck coupling of inactivated aryl fluoride/chloride using 5 W LED in a homemade photoreactor under ambient conditions. The protocol comprising metal‐free green photocatalyst tolerated a variety of aliphatic/aromatic alkenes bearing different substituents afforded good to excellent yields. The role of photogenerated excitons was confirmed by scavenger studies with K2S2O8 and EDTA. The leaching test, stability, and reusability of MBMFPc photocatalyst evidenced as a perfect heterogeneous photocatalyst and afford appreciable yield (80 %) after 5 cycles. A plausible mechanism for photocatalytic C−C coupling has been proposed and described. A metal‐free acid‐functionalized ionic liquid‐based MBMFPc photocatalyst with appreciable TON (4,51,948) and TOF (22,597 h−1) could gain significant attraction as a green catalyst in the pharmaceutical industries for the synthesis of intermediates by C−C coupling using commercial aryl chlorides.

Fe-Promoted C-F Activation of Aryl Fluorides Enables Heck-Type Coupling with Alkenes and One-Pot Synthesis of Indenes

“…33,34 However, despite all the advances shown and not shown above, to date the only reported cross-coupling reaction between an aryl fluoride and an alkene was catalyzed by a metal-free porphyrin trimer catalyst in a heterogenous reaction, yielding a Z-product in the only example examined. 35 Hence, here we report the first homogenous Heck-type coupling reaction with aryl fluorides, which is enabled by SNAr activation of aryl fluoride C-F bonds by the metallanucleophile, [CpFe(CO)2] -(Fp -).…”

Fe-Promoted C–F Activation of Aryl Fluorides Enables Heck-Type Coupling with Alkenes and One-Pot Synthesis of Indenes

“…33,34 However, despite all the advances shown and not shown above, to date, the only reported cross-coupling reaction between an aryl fluoride and an alkene was catalyzed by a metal-free porphyrin trimer catalyst in a heterogeneous reaction, yielding a Z-product in the only example examined. 35 Hence, here we report the first homogeneous Heck-type coupling reaction with aryl fluorides, which is enabled by S N Ar activation of aryl fluoride C−F bonds by the metallanucleophile, [CpFe(CO) 2 ] − (Fp − ). Moreover, we also present a one-pot synthesis of indene derivatives by coupling aryl fluorides with alkynes, thus expanding the limits of C−F activation.…”

“…The Mizoroki–Heck reaction, a palladium-catalyzed C–C coupling between aryl halides and activated alkenes, is among the most researched and broadly utilized coupling techniques, and it was one of three reactions recognized with the 2010 Nobel Prize. , However, despite all the advances shown and not shown above, to date, the only reported cross-coupling reaction between an aryl fluoride and an alkene was catalyzed by a metal-free porphyrin trimer catalyst in a heterogeneous reaction, yielding a Z-product in the only example examined . Hence, here we report the first homogeneous Heck-type coupling reaction with aryl fluorides, which is enabled by S N Ar activation of aryl fluoride C–F bonds by the metallanucleophile, [CpFe­(CO) 2 ] − (Fp – ).…”