Mechanoredox/Nickel Co-Catalyzed Cross Electrophile Coupling of Benzotriazinones with Alkyl (Pseudo)halides

A mechanochemical [2+2+2] cycloaddition facilitated by a cobalt(ii) catalyst and piezoelectric materials

In this study, we present the first general mechanochemical protocol for the catalytic [2+2+2] cycloaddition of alkynes via a simple and inexpensive cobalt(ii)-based catalytic system. The key to achieving the high efficiency of this mechanochemical transformation is the use of piezoelectric BaTiO3 as a reductant in combination with an amine additive to facilitate the generation of a catalytically active low-valent cobalt species. This method is characterized by a broad substrate scope, short reaction times, solvent-less conditions, and the feasibility of reacting poorly soluble substrates. Thus, we provide a more efficient, broadly applicable, and sustainable alternative to existing solution-based protocols.

Synthesis of N-Aryl and N-Alkyl Phthalimides via Denitrogenative Cyanation of 1,2,3-Benzotriazin-4(3H)-ones

An efficient metal-free approach for synthesizing N-aryl- and N-alkyl phthalimide derivatives from 1,2,3-benzotriazin-4(3H)-ones is described. The reaction likely proceeds via a denitrogenative cyanation pathway, utilizing TMSCN as the cyanide source. This method is straightforward as well as scalable and supports a wide range of substrates with high functional group tolerance, yielding diverse phthalimide derivatives in good to excellent yields. The utility of this method is further highlighted by the successful synthesis of a tyrosinase inhibitor analogue in good yield.

Liquid-Assisted Grinding Enables Efficient Ni-Catalyzed, Mn-Mediated Denitrogenative Cross-Electrophile Coupling of Benzotriazinones with Benzyl Chlorides

An efficient and air-tolerant Ni-catalyzed denitrogenative cross-electrophile coupling of benzotriazinones with benzyl chlorides has been developed via liquid-assisted grinding by using Mn powders as reductant and DMF as assisting liquid in the presence of anhydrous calcium chloride. Scope and limitations of the protocol to access diarylmethanes have been demonstrated with more than 20 examples, showing acceptable tolerance to functional group and steric hindrance. Although electron-withdrawing substituents on benzotriazinone or benzyl counterparts decrease the yields significantly, a series of N-alkyl-2-benzylbenzamides, diarylmethanes bearing an ortho-carbamoyl aryl group, could be obtained in modest to good yields.

Mechanoredox-Enabled Isothiocyanation of Primary Amines Using Piezoelectric Material as the Redox Catalyst

A novel mechanoredox-enabled synthesis of aromatic and aliphatic isothiocyanates from primary amines and carbon disulfide under ball milling conditions using a piezoelectric material (BaTiO3) as the redox catalyst has been developed. This method displays several features, such as short reaction time, operational simplicity, room temperature and air conditions, minimal solvent, broad substrate scope, and recyclable cheap catalyst. Preliminary mechanistic studies revealed that highly polarized piezoelectric material acted as a single-electron transfer (SET) oxidation reagent for the key desulfurization process.

Controllable Molecular Editing of 2-Amino-N-substituted Benzamides: Site-selective Synthesis of 6-Selenylated N-Substituted 1,2,3-Benzotriazine-4(3H)-ones

We present an efficient silver-catalyzed one-pot controllable molecular editing protocol for the transformation of 2-amino-N-substituted benzamides into 6-selenylated N-substituted 1,2,3-benzotriazine-4(3H)-ones under mild reaction conditions. This three-component reaction strategy is achieved by building N-N/N═N/C-Se bonds, which provides a practical pathway for the preparation of selenylated 1,2,3-benzotriazine-4(3H)-ones with a broad substrate scope and good functional group tolerance, as well as high site-selectivity. Mechanistic experiments suggest that this reaction proceeds via intermolecular site-selective C-H selenylation of 2-amino-N-substituted benzamides with readily available diselenides, followed by annulation of selenylated 2-amino-N-substituted benzamides using AgNO3 as the nitrogen synthon.

Mechanochemical Radical Transformations in Organic Synthesis

Organic synthesis has historically relied on solution-phase, polar transformations to forge new bonds. However, this paradigm is evolving, propelled by the rapid evolution of radical chemistry. Additionally, organic synthesis is witnessing a simultaneous resurgence in mechanochemistry, the formation of new bonds in the solid-state, further contributing to this shift in the status quo. The aforementioned advances in radical chemistry have predominantly occurred in the solution phase, while the majority of mechanochemical synthesis advances feature polar transformations. Herein, we discuss a rapidly advancing area of organic synthesis: mechanochemical radical reactions. Solid-state radical reactions offer improved green chemistry metrics, better reaction outcomes, and access to intermediates and products that are difficult or impossible to reach in solution. This review explores these reactions in the context of small molecule synthesis, from early findings to the current state-of-the-art, underscoring the pivotal role solid-state radical reactions are likely to play in advancing sustainable chemical synthesis.

Photoredox Catalyzed Tandem Denitrogenative [4 + 2] Annulation of 1,2,3-Benzotriazin-4(3H)-ones with Terminal Olefins

The dihydroisoquinolones skeleton is ubiquitous in natural products and biological molecules. Reported strategies for constructing dihydroisoquinolones usually require noble metal catalysts or stoichiometric oxidants, which limit their wide applications. Herein, we developed a photoredox catalyzed tandem denitrogenative [4 + 2] annulation reaction of 1,2,3-benzotriazin-4(3H)-ones with terminal olefins. A variety of dihydroisoquinolones can be accessed in moderate to excellent yield. This protocol features high atom-economy, mild reaction conditions, and is external oxidant-free, enabling the synthesis of various substituted dihydroisoquinolones.

Organic Reactions Enabled by Mechanical Force-Induced Single Electron Transfer

Mechanochemical reactions, achieved through milling, grinding, or other mechanical actions, have emerged as a solvent-free alternative to traditional solution-based chemistry. Mechanochemistry not only provides the opportunity to eliminate bulk solvent use, reducing waste generation, but also unveils a new reaction strategy which enables the realization of reactions previously inaccessible in solution. While the majority of organic reactions facilitated by mechanical force traditionally follow two-electron transfer pathways similar to their solution-based counterparts, the field of mechanochemically induced single-electron transfer (SET) reactions has witnessed rapid development. This review outlines examples of mechanochemical reactions facilitated by the SET process, focusing on the reagents that initiate SET, thereby positioning mechanochemistry as a burgeoning field within the realm of single-electron chemistry.