Copper-Catalyzed Reductive Alkylation of β-Acyl Allylic Thioethers with Alkyl Bromides to Access α-Branched Enones with Flexible Alkyl Chains

Replacing alkyl organometallic reagents with alkyl bromides to achieve desulfurative alkylation of thioethers has been a long-standing challenge in desulfurative functionalization of organosulfur compounds. Herein, we report a copper-catalyzed reductive tertiary alkylation of β-acyl allylic sulfides with α-carbonyl alkyl bromides under mild reaction conditions. The reaction accommodates a broad substrate scope with good functional group compatibility, providing a direct route to install diversified (sp3)-carbon quaternary centers at the allylic position of α-branched enones. Further synthetic applications of this protocol have been demonstrated with scale-up experiments and late-stage modification of the products.

A Completely Metal-Free Protocol for Oxidative Desulfitative C-N Coupling Reaction in Non-Basic Condition

A metal free oxidative desulfitative C-N coupling reaction through activation of latent thiol group using hypervalent iodine reagent is being reported in eco-friendly solvent ethanol. Here, the thio-amide group present in 5-alkylidene-rhodanine has been utilized as latent thiol functionality and C-N coupling with amines is realized. The reaction occurs evading the use of metal catalysts, inert atmosphere, high temperature or microwave heating, and strong base which is normally required for metal catalyzed C-N coupling reaction. Pertinently, here poorly nucleophilic aromatic amines react very efficiently. Desulfitative C-N coupling involving free thiol moiety and poorly nucleophilic aromatic amines in metal free condition has never been accomplished in one step, without requiring high temperature microwave heating or strong bases. The reaction occurs at just 50 °C in few hours under ambient atmosphere. Moreover, here no H2S is released in the environment, since solid sulphur is precipitated out as side product, making this protocol environmentally friendly. Metal free condition, low temperature, use of non-toxic solvent and reagent, prevention of the release of H2S in the environment make this protocol very much environmentally friendly and highly suitable for C-N coupling in a sustainable way.

Desulfurative Functionalization of β-Acyl Allylic Sulfides with N-H Free Indoles Highly Regioselective at C3 and N1 Positions: Rapid Access to α-Branched Enones

A regiodivergent allylation of 1H-indoles highly selectively at the C3 and N1 positions with β-acyl allylic sulfides through desulfurative C-C/C-N bond-forming reactions has been developed under mild conditions. Notably, the remarkable site-selective switch can be achieved by a delicate choice of solvents and bases. This cost-efficient method displays a broad substrate scope, good functional compatibility, and excellent site-selectivity, thus offering a divergent synthesis of indole substituted α-branched enones, which possess diverse potential opportunities for further applications and derivatization.