Iron And Nickel Catalysis Of Air Oxyalkylenes To Synthesize Ketones And Aldehydes

The transition metal catalyzed oxidation of olefins to carbonyl compounds has been widely applied in the synthesis of pharmaceuticals,commercial chemicals,and natural products.Wacker oxidation is one of the most important methods.The reason why it is researched and applied is closely related to its own advantages:(1)readily available,inexpensive,and thermally-,air-and water-stable substrates;(2)wide applicability to a broad range of substrates;(3)high yield and efficiency.The traditional Wacker oxidation is the use of palladium salt as a catalyst and copper chloride as an oxidant to oxidize the alkenes to aldehydes or ketones in air.With the demand for green synthesis,the traditional Wacker oxidation shows many limitations,such as the decomposition of palladium catalysts,the isomerization of olefins,the formation of chlorine-containing by-products,and copper salt contamination.Therefore,exploring a green and economical Wacker type oxidation has great application prospects.Although iron-catalyzed oxidation of C-C bond cleavage to aldehydes or ketones has been developed,the selectivity and the reactivity are still unmet challenges.Our work includes three parts:(1)the development of iron-catalyzed Wacker type oxidation reaction.(2)the development of nickel-catalyzed isomerization-Wacker type oxidation.(3)the development of iron-catalyzed oxidation of C-C bond cleavage to arylaldehydes.The main results of our research are summarized as follows:1.An iron-catalyzed Wacker-type oxidation reaction has been demonstrated.The reaction conditions were optimized by the oxidation of 4-phenyl-1-butene in the air as a template reaction.The optimal conditions were:ferrous acetylacetonate as a catalyst,tert-butanol as a solvent,PMHS(polymethylhydrosiloxane)as a reducing agent,RT.Under the optimal conditions,the substrate expansion of olefins was carried out.The yields of most target products were between 50-80%,and the reaction mechanism was also studied.2.A nickel-catalyzed isomerization Wacker type oxidation reaction has been developed.The reaction conditions were optimized by the oxidation of 4-allyl anisole in air as a template reaction to obtain the optimal conditions:nickel bromide as catalyst,4,4'-dimethyl-2,2'-bipyridyl as ligand,ethanol as solvent,PMHS(polymethylhydrosiloxane)as additive,RT.A series of substrate extensions were performed under optimal conditions.It was found that the method has good functional group compatibility and is suitable for some natural product structures.The yield of the target product is between 60-99%.At the same time,the mechanism of the reaction was also explored.3.An iron-catalyzed oxidation reaction of the C-C bond cleavage to the aromatic aldehydes has been disclosed.The reaction conditions were optimized by the oxidation of 4-allyl anisole in air as a template reaction to obtain the optimal conditions:ferric nitrate nonahydrate as the catalyst,ethanol as a solvent,TMDSO(1,1,3,3-tetramethyldisiloxane)as reducing agent,RT.Under the optimal conditions,the substrate was expanded.The results show that the method has good functional group compatibility and is suitable for more complex substrates.The yield of the target product is between 55-95%.In addition,a preliminary study of the mechanism of the reaction was also conducted.