Palladium-catalyzed synthesis of pyrimidine substituted diaryl ethers through Suzuki Miyaura coupling reactions: Experimental and DFT studies

Abstract

Aryl and hetero-aryl substituted pyrimidine derivatives demonstrate widespread applications in nonlinear optics (NLO), agrochemical and therapeutic drugs. Therefore, 2-(4-phenoxyphenyl)pyrimidine (2-PPP) and 5-(4-phenoxyphenyl) pyrimidine (5-PPP) were synthesized by palladium-catalyzed Suzuki coupling approach. The structure elucidation of synthesized products was done by 1H-NMR, 13C-NMR, and UV–vis spectroscopic analyses. The natural bond orbital (NBO) analysis was performed using density functional theory (DFT) assisted M06/6-311G** functional, which confirmed the existence of delocalization process and the hyper-conjugative interaction with representative transitions as π(C10-N16)→π*(C14-N17) and π(C26-N30)→π*(C9-N31) having stabilization energies of 36.30 and 36.55 kcal/mol for 2-PPP and 5-PPP, respectively. The small energy ΔE LUMO HOMO gap as 5.330 eV in 2-PPP and 4.975 eV in 5-PPP was evident from the frontier molecular orbital (FMO) analysis, computed at TD-DFT/M06/6-311G** level, Both the NBO and the FMO analysis predicted promising NLO molecular response. Furthermore, HF, LC-BLYP, CAM-B3LYP, M06-2X, and M06 methods, along with the 6-311G** basis set, were utilized to acquire the NLO findings of 2-PPP and 5-PPP. M06 and HF methods indicated the largest and lowest values of average polarizability ⟨α⟩ and first hyperpolarizability (βtot), respectively for both the compounds 2-PPP and 5-PPP. The ⟨α⟩ and βtot values of 2-PPP and 5-PPP were observed as 7.0 and 7.3 times and 15 and 36 times higher than the urea molecule, respectively. Both compounds hold fine NLO characteristics, thus recommended for future NLO applications.