Efficient base-free hydrodehalogenation of organic halides catalyzed by a well-defined diphosphine-ruthenium(II) complex

Ruthenium/HI-catalyzed direct hydromethylation of indoles and quinolines in DME

“…Our prior research has shown that Ru1 is an effective and robust catalyst for hydrogenation of CO 2 39 and hydrodehalogenation of organic halides. 40 Building on these results, we extended the application of direct hydromethylation of N-heterocycles using Ru1 as a catalyst. To investigate the impact of additives on the chemoselectivity of hydromethylation, initial experiments were performed using indole ( a1 ) as the substrate (Table 1).…”

“…With regard to the hydrogenation process (Scheme 3), based on our recent work concerning the hydrodehalogenation of Ar–X with Ru1 , 40 the ruthenium active species ( III ) could be formed when Ru1 was treated with H 2 in DME. Then, an N-heterocycle molecule ( a1 or II1 ) approaches III to form an intermediate IV and directly transfers a hydride from the Ru center to its unsaturated carbon and along combines with hydrogen ion from the solvent to form a saturated heterocycle ( b1 or I1 ) and cationic species V , subsequently active species III is re-formed via the reduction of V by the heterolytic cleavage of H 2 .…”

“…Like the organic halide hydrodehalogenation with Ru1 , there is an active Ru-hydride species in the N-heterocycle hydrogenation. 40 Regarding the indole hydromethylation, the N -methylation process and the hydrogenation process occur in parallel, but for the hydromethylation of quinolines hydrogenation occurs first and then N -methlylation occurs. More importantly, this work provides a concise, effective, synthetic methodology for the production of N -methyl saturated N-heterocycles.…”

Reductive Hydrodehalogenation of Halogenated Carboxylic Acid Derivatives Using a DMSO/HCOONa·2H2O System

“…Due to these important applications, the development of facile and efficient methods for hydrodehalogenation has attracted considerable attention from organic chemists over the past several decades. Conventional methods for hydrodehalogenation of aryl halides generally involve radical reductive dehalogenation using AIBN as an initiator; transition metal-catalyzed reductions using reducing agents such as H 2 , hydrosilanes, hydrides, and alcohols; electrolysis-promoted dehalogenation of aryl or alkyl halides using a metal electrode to supply an electron or using amines as terminal reductants and hydrogen atom donors; , and visible-light-induced dehalogenation in the presence of organic or inorganic photocatalysts, together with a variety of additives, including strong bases, sodium formate, thiols, disulfides, amides, and amines. , However, these methods suffer from their own limitations, such as the poor selectivity leading to low yields, harsh reaction conditions, the use of an expensive noble metal together with an inert atmosphere and essential ligands, excess amounts of potentially hazardous radical initiators, and special photo/electrochemical reactors. Although the metal-free hydrodehalogenation of aryl halides through a radical chain pathway has also been developed, additives covering strong bases (e.g., t -BuOK and NaH) together with electron donors (e.g., 1,10-phenanthroline) and hydrogen sources (e.g., alcohol) are still required .…”