Peter Becker

Mechanochemical Iridium(III)-Catalyzed C-H Bond Amidation of Benzamides with Sulfonyl Azides under Solvent-Free Conditions in a Ball Mill.

Mechanochemical conditions have been applied to an iridium(III)-catalyzed C-H bond amidation process for the first time. In the absence of solvent, the mechanochemical activation enables the formation of an iridium species that catalyzes the ortho-selective amidation of benzamides with sulfonyl azides as the nitrogen source. As the reaction proceeds in the absence of organic solvents without external heating and yields the desired products in excellent yields within short reaction times, this method constitutes a powerful, fast, and environmentally benign alternative to the common solvent-based standard approaches.

Copper-Catalyzed Oxidative Decarboxylative Couplings of Sulfoximines and Aryl Propiolic Acids

A method has been developed for the preparation of N-alkynylated sulfoximines involving the copper-catalyzed decarboxylative coupling of sulfoximines with aryl propiolic acids. A range of substituents on both the sulfoximidoyl moiety and the aryl group of the propiolic acid were compatible with this reaction process to afford a series of sulfoximidoyl-functionalized alkynes.

Mechanochemical Rhodium(III)-Catalyzed CH Bond Functionalization of Acetanilides under Solventless Conditions in a Ball Mill†

In a proof-of-principle study, a planetary ball mill was applied to rhodium(III)-catalyzed C-H bond functionalization. Under solventless conditions and in the presence of a minute amount of Cu(OAc)2, the mechanochemical activation led to the formation of an active rhodium species, thus enabling an oxidative Heck-type cross-coupling reaction with dioxygen as the terminal oxidant. The absence of an organic solvent, the avoidance of a high reaction temperature, the possibility of minimizing the amount of the metallic mediator, and the simplicity of the protocol result in a powerful and environmentally benign alternative to the common solution-based standard protocol.

Acylsilanes in Rhodium(III)‐Catalyzed Directed Aromatic C–H Alkenylations and Siloxycarbene Reactions with CC Double Bonds

Acylsilanes are known to undergo a 1,2-silicon-to-oxygen migration under thermal or photochemical conditions to form siloxycarbenes. However, there are few reports regarding the application of siloxycarbenes in organic synthesis and surprisingly, their reaction with CC double or triple bonds remains virtually unexplored. To facilitate such a study, previously inaccessible aromatic acylsilanes containing an ortho-tethered CC double bond were identified as suitable substrates. To access these key intermediates, we developed a new synthetic method utilizing a rhodium-catalyzed oxidative Heck-type olefination involving the application of an acylsilane moiety as a directing group. When exposed to visible-light irradiation, the ortho-olefinated acylsilanes underwent a smooth intramolecular cyclization process to afford valuable indanone derivatives in quantitative yields. This result paves the way for the development of new transformations involving siloxycarbene intermediates.

Cooperative Light-Activated Iodine and Photoredox Catalysis for the Amination of Csp3-H Bonds

Abstract An unprecedented method that makes use of the cooperative interplay between molecular iodine and photoredox catalysis has been developed for dual light‐activated intramolecular benzylic C−H amination. Iodine serves as the catalyst for the formation of a new C−N bond by activating a remote Csp3 −H bond (1,5‐HAT process) under visible‐light irradiation while the organic photoredox catalyst TPT effects the reoxidation of the molecular iodine catalyst. To explain the compatibility of the two involved photochemical steps, the key N−I bond activation was elucidated by computational methods. The new cooperative catalysis has important implications for the combination of non‐metallic main‐group catalysis with photocatalysis.

Exploring the reactivity of N-alkynylated sulfoximines: [2 + 2]-cycloadditions.

To assess the potential of N-alkynylated sulfoximines as new (chiral) reagents for organic synthesis, their reactivity profile in numerous synthetic processes is under investigation. When reacted with ketenes, the alkynylated-sulfoximines undergo a [2 + 2]-cycloaddition process to afford sulfoximine-functionalized cyclobutenones in excellent yields.

Synthesis of Sulfoximidoyl-Containing Hypervalent Iodine(III) Reagents and Their Use in Transition-Metal-Free Sulfoximidations of Alkynes

Well-defined hypervalent iodine(III) reagents incorporating transferable sulfoximidoyl groups were obtained through ligand exchange reactions of methoxy(tosyloxy)iodobenzene (MTIB) with NH sulfoximines in good to excellent yields. The solid-state structure of a representative product was characterized by X-ray crystallography. Utilizing these reagents in synthesis provides a new, transition-metal-free approach towards N-alkynylated sulfoximines.

Acylsilanes in Iridium‐Catalyzed Directed Amidation Reactions and Formation of Heterocycles via Siloxycarbenes

Exposing ortho-amido aroylsilanes to visible light or heat leads to cyclization reactions that provide N-heterocyclic compounds via siloxycarbenes as key intermediates. The previously unreported starting materials have been prepared by directed amidations of aromatic acylsilanes in the presence of an iridium catalyst followed by N-alkylation.

Exploring the Reactivity of N-Alkynylated Sulfoximines: Regioselective Hydroacyloxylations and Hydroaminations.

N-Alkynylated sulfoximines undergo smooth transformations with benzoic acids and sulfonamides under mild conditions affording the corresponding hydroacyloxylation or hydroamination products. The transformations proceed in the absence of catalysts or additional reagents in short reaction times generating the products in excellent yields and very high stereoselectivities.

Exploring the Reactivity of N -Alkynylated Sulfoximines: Acid-Catalyzed Cyclizations

N-Alkynylated sulfoximines undergo acid-promoted cyclization processes under mild reaction conditions. The transformations proceed in short reaction times affording sulfoximidoyl-functionalized naphtho[2,1-b]thiophenes or pyrrolo[1,2-a]quinolines in up to excellent yields.