Air-Stable Phosphine-Free Ruthenium(II) Catalyst for Acceptorless Dehydrogenation and Related Transformations: A Sustainable Approach

Catalytic acceptorless dehydrogenation for producing carbonyl compounds has recently emerged as a viable alternative to traditional stoichiometric reagents used in the oxidation of alcohols. Herein, we have developed an effective and sustainable approach for the synthesis of carbonyl compounds from the respective alcohols through catalytic acceptorless dehydrogenation under ambient conditions. The present approach utilizes a phosphine-free, air-stable Ru(II) complex (ARP-03), marking a novel contribution to this field, to the best of our knowledge. This concept was further extended to the synthesis of carboxylic acids and N-alkyl amines and demonstrates a broad substrate range, producing yields that vary from good to excellent with low catalyst loading. The current process involves the release of molecular hydrogen and water as the sole byproducts, making it environmentally benign. The mechanistic insights, supported by ESI-MS, and liberation of H2 gas by the in situ hydrogenation of 3-pyridin-2-yl-acrylic acid tert-butyl ester offer a more profound understanding of the reaction pathway. The application of ARP-03 for the synthesis of value-added products nitrofurantoin (antibacterial), methaphenilene (antihistamine), tripelennamine (antihistamine), and thonzylamine (antihistamine) has been demonstrated. This work provides an industrially feasible and safer approach to the oxidation of alcohol, paving the way for future applications.