Oxygen Vacancy Mediated Reactivity of CaO/CuO Composite for the Synthesis of Amino-N-heterocycles

Utilising the oxygen-vacancy-mediated reactivity of CaO/CuO and hydrazine monohydrate in isopropyl alcohol at 353 K, a variety of amino-derivatives of N-heterocycles, including pyridine, indole, quinoline, isoquinoline, and benzothiazole, have been selectively synthesised by reducing their nitro analogues. It is demonstrated that CaO/CuO composite is a reusable, solvent-resilient solid reducing agent that can reduce a variety of nitro-N-heterocyclic substrates. The critical role of the structure of CaO/CuO on the nitro-reduction activity has been studied using spectroscopy and microscopy. DFT simulations indicate the facile formation of oxygen vacancies (EO,vac=-43.4 kJ/mol) on the interface of CaO/CuO surface under reducing environment. The presence of CaO facilitated a stronger interaction of the nitro-substrate on the oxygen vacant CuO (111) surface, resulting into a significantly lower activation energy (Ea=21.9 kJ/mol) for N-O dissociation. The reaction could be scaled up from 1 to 12 mmol of substrate. CaO/CuO is a reusable and a cost-effective alternative to the conventional catalyst (Pd/C, Pt/C). Utilising the oxygen-vacancy-mediated reactivity of CaO/CuO and hydrazine monohydrate in isopropyl alcohol at 353 K, a variety of amino-derivatives of N-heterocycles, including pyridine, indole, quinoline, isoquinoline, and benzothiazole, have been selectively synthesised by reducing their nitro analogues.image

Automated summary

By utilizing the oxygen-vacancy-mediated reactivity of CaO/CuO and hydrazine monohydrate in isopropyl alcohol, a variety of amino-derivatives of N-heterocycles have been selectively synthesized by reducing their nitro analogues. The CaO/CuO composite is found to be a reusable and solvent-resilient solid reducing agent that shows promising results as an alternative to conventional catalysts.