Concise access to perimidines by palladium (II) complexes via acceptorless dehydrogenative coupling of alcohols

Abstract

A facile protocol for the one‐pot synthesis of 2,3‐dihydro‐1H‐perimidines via dehydrogenative coupling of easily exploitable benzyl alcohols supported by new Pd(II) complexes has been reported. To accomplish the construction of perimidines, a new set of palladium(II) complexes [Pd(L)Cl (PPh3)] (1–3) encompassing biphenyl benzhydrazone ligands (L=L1–L3) has been reported as catalysts. Structural characterization by elemental analysis, FT‐IR, NMR (1H and13C), and mass spectral analyses confirmed the composition of synthesized complexes. The molecular structures complex1and complex2were unequivocally resolved using single‐crystal X‐ray diffraction. It reveals that the complex espoused distorted square‐planar geometry around Pd(II) ion chelated by azomethine nitrogen and imidolate oxygen of biphenyl benzhydrazone ligands with labile chloride and a triphenylphosphine. Further, the selective synthesis of a broad range of functionalized perimidines has been accomplished via ADC of a variety of alcohols with 1,8‐diamino naphthalene. The palladium complexes mediated catalytic synthesis offered good yields of perimidines up to 86% using only 0.5 mol% catalyst loading. A probable mechanism to the formation of perimidines was postulated from the results of control experimental investigations. The environmentally compassionate, greener ADC protocol progresses via the generation of aldehyde intermediate and releases only water and hydrogen gas.