Application Of N-formyl Ethylenediamine Derivatives In Metal Catalysis And Organic Synthesis

N-Heterocyclic carbine precursor imidazolium salts are widely used in catalysis,medicine and materials,and have developed rapidly in the last two decades,becoming one of the most important structures in organic synthesis.N-formyl ethylenediamine compounds are the hydrolysis products of N-heterocyclic carbine precursor imidazolium salts,which are usually treated as by-products,increasing the cost of their post-processing.However,N-formyl ethylenediamine compounds are simple to prepare and easy to store.In recent years,the conversion of waste or raw materials with low value into products with high added value has been a hot topic of interest for organic synthetic chemists.In this thesis,we will review the development applications of N-formyl ethylenediamine compounds and the synthesis methods of N-heterocyclic carbine-Ni complexes,and we have carried out some research work around this field as follows:Firstly,five multi-dentate N-heterocyclic carbine-Ni complexes were synthesized for the first time by an in situ closed-loop strategy in high yields of 29-85%based on the N-formyl ethylenediamine produced by the hydrolysis of pyridinylbenzimidazole salts developed by our group as a starting material,and their structures were characterized by single-crystal diffraction.The method can be performed under air and is easy to operate.The series of Ni complexes can catalyze the Suzuki coupling reaction of allyl alcohols with aryl boronic acids efficiently,and are compatible with allyl alcohols and aryl boronic acid substrates of different substituents,yielding 28 allyl aromatic products,and the reactions can be scaled up to the gram scale.Next,the above synthesized N-heterocyclic carbine-Ni complexes were applied to catalyze the reactions ofα,β-unsaturated carbonyl compounds.The carbonyl-selective reduction ofα,β-unsaturated carbonyl compounds was achieved by using inexpensive borane ammonia complexes as reducing agents to avoid the reduction ofα,β-unsaturated ketones to alcohols,further improving their atomic and step economy.Subsequently,we again extended the application of N-formyl ethylenediamine compounds to synthesize20 pyridinyl benzimidazole thione derivatives by addition with sulfur powder under mild conditions.Exploration of the activity pattern of the substrates revealed that the process generated N-heterocyclic carbin intermediates,and thus the N-formyl ethylenediamine could serve as an abundant class of carbin precursors.Secondly,the selective synthesis of benzimidazolones（30 examples）and pyridylbenzodiazepines（24examples）was achieved under the conditions of bases Na OAc and Na HCO₃,respectively,using inexpensive and available K₂S₂O₈ as the oxidant,and their synthesis and further functionalization modifications were successfully carried out on a gram scale.Finally,two new methods for the synthesis of gem-dihaloenones have been developed using inexpensive alkynes,polyhalomethanes,water or alcohols as starting materials under the promotion of visible light.The method,which does not require the use of photocatalysts and any additives,exhibits good substrate generality,efficiently constructs 43 gem-dihaloenones and achieves gram-scale preparation in high yields（71-81%）.It is worth mentioning that the reaction is compatible with a variety of alcohol solvents,highlighting the green and practical nature of the method.The mechanistic investigation showed that the formation of tertiary carbon-centered radicals is crucial to generate products viaβ-scission.