Synthesis of Pyrimidines and Quinazolines via Acceptorless Dehydrogenative Coupling Catalyzed by PNN-Pd Complex

In this study, we report the catalytic application of PdIIPNN [PNN: 2,6-{(R2P)N(H)(C5H3N)(C2HN3C6H5)}] (L1 R = Ph; L2 R = tBu) pincer complexes (Pd1-Pd4) for the sustainable and cost-effective synthesis of pharmacologically important pyrimidines and quinazolines by acceptorless dehydrogenative coupling of alcohols. Among four mixed donor PdII aromatized and dearomatized complexes, [PdCl{RPHNN-kappa 3-P,N,N]Cl and [PdCl{RPNN}-kappa 3-P,N,N] (R = Ph or tBu), tert-butylphosphinyl complex was found to be more efficient in the catalytic reactions. A wide range of substituted pyrimidine (45 examples) derivatives was synthesized from amidine, benzyl alcohols and ketones using Pd2 (0.1 mol%) in toluene at 110 degrees C. Further, the catalyst was found to be effective for the synthesis of quinazolines (22 examples) using 2-aminobenzyl alcohols and benzonitriles. HRMS and NMR studies confirmed reactions proceeding through Pd-alkoxide and Pd-hydride intermediates.