Pyridinium-based carboxyl-functionalized porphyrin: an easy gateway to afford substituted benzyl aryl ethers

Abstract

The formation of substituted benzyl aryl ethers is one of the vital industrial methods to generate pharmaceutically important intermediates and value-added compounds. Herein, the etherification of furfuryl ethyl ether was effectively carried out using a pyridinium-based carboxyl-functionalized porphyrin (PCFPc) photocatalyst under 5 W LED light irradiation. This is the first metal-/base-free protocol tolerating a variety of activated/inactivated aryl halides and benzyl alcohols to afford benzyl aryl ethers in appreciable yields (53–74%) in a lab-made photo-chamber under ambient reaction conditions. The novel PCFPc photocatalyst was prepared and then characterized using ¹H and ¹³C NMR, FT-IR, powder XRD, XPS, and BET analyses. The proton level (H₀) and band gap were determined using UV-visible spectrophotometry, supported by cyclic voltammetry analysis. The benzyl aryl ethers were successfully obtained (74%) under the optimized reaction conditions of 15 mg photocatalyst with a 1 : 1 substrate ratio, under 5 W LED light illumination at ambient temperature for 18 h. C–O bond formation was supported by (¹H, ¹³C) NMR, DEPT-135, FT-IR and HR-MS analyses. A plausible reaction mechanism was proposed with the help of prior reports. The etherification appeared to progress via the formation of an aryl radical supported by a TEMPO scavenger. The proposed technique is simple and highly effective, and it comprises an easy separation of the photocatalyst and analysis to attain the desired product.