Transition-Metal-Free Catalytic Formal Hydroacylation of Terminal Alkynes

Photoinduced, Metal-Free Hydroacylation of Aromatic Alkynes for Synthesis of α,β-Unsaturated Ketones via C(sp3)-H Functionalization

Despite the notable advancements made over the past decade in achieving carbon-carbon bonds by transition-metal-catalyzed cross-coupling processes, metal-free cross-coupling reactions for hydroacylation of aromatic alkynes via C(sp3)-H functionalization are still rare and highly desired. Here we report a metal-free reliable approach for the synthesis of α,β-unsaturated ketones (chalcones) via C(sp3)-H functionalization using MeCN:H2O as green solvent, Eosin Y as organic photocatalyst, and ambient air as oxidant. More significantly, this strategy can effectively transform a variety of methyl arenes and aromatic alkynes into the desired product. With high atom efficiency, use of green solvents, metal-free nature, environmental friendliness, and visible light as a renewable energy source, this method is compatible with biologically active molecules.

Conceptual advances in nucleophilic organophosphine-promoted transformations

Catalysis by trivalent nucleophilic organophosphines has emerged as an essential tool in organic synthesis. Several new organic transformations promoted by phosphines substantiate and complement the existing synthetic chemistry tools. Mere design of the substrate and reagent combinations has introduced new modes of reactivity patterns, which are otherwise difficult to achieve. These design considerations have led to the rapid build-up of complex molecular entities and laid a solid foundation to synthesise bioactive natural products and pharmaceuticals. This article presents an overview of some of the conceptual advances, including our contributions to nucleophilic organophosphine chemistry. The scope, limitations, mechanistic insights, and applications of these metal-free transformations are discussed elaborately.

Distinctive Mechanistic Scenarios and Substituent Effects of Gold(I) versus Copper(I) Catalysis for Hydroacylation of Terminal Alkynes with Glyoxal Derivatives

Density functional theory (DFT) calculations have been conducted to study the mechanisms, substituent effects, and the role of bases in Au- and Cu-catalyzed hydroacylation of terminal alkyne with glyoxal derivatives. The two reactions, despite being catalyzed by the same group of transition metals, follow distinctive reaction mechanisms. Through the detailed DFT calculations, insights into the mechanisms are obtained, and the substituent effects and the role of the bases are understood.

Selective oxidation of alcohol-d 1 to aldehyde-d 1 using MnO2

The selective oxidation of alcohol-d₁ to prepare aldehyde-d₁ was newly developed by means of NaBD₄ reduction/activated MnO₂ oxidation. Various aldehyde-d₁ derivatives including aromatic and unsaturated aldehyde-d₁ can be prepared with a high deuterium incorporation ratio (up to 98% D). Halogens (chloride, bromide, and iodide), alkene, alkyne, ester, nitro, and cyano groups in the substrates are tolerated under the mild conditions.

A facile method for deutrium incorporation into aldehydes by mild reduction of NaBD₄ of aldehydes and MnO₂ oxidation (98% D) is disclosed.

Sequential Catalytic Functionalization of Aryltriazenyl Aldehydes for the Synthesis of Complex Benzenes

We demonstrate that aryltriazenes can promote three distinctive types of C–H functionalization reactions, allowing the preparation of complex benzene molecules with diverse substitution patterns. 2-Triazenylbenzaldehydes are shown to be efficient substrates for Rh(I)-catalyzed intermolecular alkyne hydroacylation reactions. The resulting triazene-substituted ketone products can then undergo either a Rh(III)-catalyzed C–H activation, or an electrophilic aromatic substitution reaction, achieving multifunctionalization of the benzene core. Subsequent triazene derivatization provides traceless products.

New synthesis of 2-aroylbenzothiazoles via metal-free domino transformations of anilines, acetophenones, and elemental sulfur

A new synthesis of 2-aroylbenzothiazoles via iodine-promoted domino transformations of anilines, acetophenones, and elemental sulfur was demonstrated. The highlights of this tandem synthesis are (1) easily available anilines and acetophenones as feedstock; (2) transition metal-free conditions; (3) inexpensive, nontoxic, easy handling, and abundant elemental sulfur as a building block. This synthetic strategy would complement the existing methods in the synthesis of this important heterocyclic scaffold. To our best knowledge, the formation of 2-aroylbenzothiazoles from simple anilines, acetophenones, and elemental sulfur was not previously reported in the literature.

A new synthesis of 2-aroylbenzothiazoles via iodine-promoted domino transformations of anilines, acetophenones, and elemental sulfur was demonstrated.