Nickel-Catalyzed Denitrogenative Cross-Coupling Reaction of 1,2,3-Benzotriazin-4(3H)-ones with Organoboronic Acids: An Easy Access to Ortho-Arylated and Alkenylated Benzamides

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.

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.

Metal-catalyzed divergent synthesis from ylides with 3-arylbenzo[d][1,2,3]triazin-4(3H)-ones

The present work reveals a new metal-catalyzed synthetic reaction involving 1,2,3-benzotriazinones with carbonyl sulfoxonium ylide and iodonium ylide, resulting in divergent products. Within this catalytic system, 3-phenylbenzo[d][1,2,3]triazin-4(3H)-one derivatives undergo C-H alkylation processes facilitated by a Cp*Rh(III) catalyst when combined with a carbonyl sulfoxonium ylide. On the other hand, when iodonium ylide substrates are used, they undergo an alkenylation reaction facilitated by a Cp*Ir(III) catalyst. In addition, hydrazone products are produced by synthesizing iodonium ylide substrates with the use of a copper catalyst. These transformations demonstrate mild reaction conditions, a wide range of substrates, and excellent compatibility with various functional groups. The strategy and tactics utilized have been effectively implemented on a significant scale.

Ru(II)-Catalyzed C-H Amination of 1,2,3-Benzotriazinones with Azide Compounds

A Ru(II)-catalyzed directed C-H amination of 1,2,3-benzotriazinones with azide compounds has been reported. The reaction has a wide substrate scope of organic azides with good results and represents a useful pathway to the construction of versatile heterocyclic amino products. In addition, the method can be used for the phthalazinones, highlighting the synthetic practicability of the strategy.

Continuous Flow Synthesis of Benzotriazin-4(3H)-ones via Visible Light Mediated Nitrogen-Centered Norrish Reaction

We report a new protocol for the synthesis of substituted benzotriazin-4(3H)-ones which are underrepresented heterocyclic scaffolds with important pharmacological properties. Our method exploits acyclic aryl triazine precursors that undergo a photocyclization reaction upon exposure to violet light (420 nm). Continuous flow reactor technology is exploited to afford excellent yields in only 10 min residence time with no additives or photocatalysts needed. The underlying reaction mechanism appears to be based on an unprecedented variation of the classical Norrish type II reaction with concomitant fragmentation and formation of N-N bonds. Scalability, process robustness, and green credentials of this intriguing transformation are highlighted.

Regioselective Synthesis of 3-Substituted Isocoumarin-1-imines via Palladium-Catalyzed Denitrogenative Transannulation of 1,2,3-Benzotriazin-4(3H)-ones and Terminal Alkynes

A palladium-catalyzed denitrogenative transannulation strategy to access various 3-substituted isocoumarin-1-imine frameworks using 1,2,3-benzotriazin-4(3H)-ones and terminal alkynes is described. The reaction is highly regioselective and tolerates a wide range of functional groups. The reaction is believed to proceed via a five-membered palladacycle intermediate extruding environmentally benign molecular nitrogen as a by-product. The utility of this method was showcased through the one-pot synthesis of biologically relevant 3-substituted isocoumarin scaffolds.

1,2,3-Benzotriazine Synthesis by Heterocyclization of p-Tosylmethyl Isocyanide Derivatives

An efficient methodology to form 4-alkoxy- and 4-aryloxybenzo[d][1,2,3]triazines via an intramolecular heterocyclization of 1-azido-2-[isocyano(p-tosyl)methyl]benzenes under basic conditions has been developed. DFT calculations have been performed to further understand the mechanism of this heterocyclization, which occurs in good to excellent yields with a broad scope.

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

An air-tolerant mechanoredox/nickel cocatalyzed cross electrophile coupling of benzotriazinones with alkyl (pseudo)halides is developed by liquid-assisting grinding in the presence of manganese powders and strontium titanate as a reductant and a cocatalyst, respectively. Mechanical activation of metal surfaces via ball milling eliminates the chemical activator for manganese, while mechanoredox cocatalysis of strontium titanate remarkably improves the aryl/alkyl cross electrophile coupling via piezoelectricity-mediated radical generation from alkyl halides. Both benzotriazinones and alkyl (pseudo)halides display reactivities in the mechanoredox/nickel cocatalysis different from those of conventional thermal chemistry in solution. The scope of the reaction is demonstrated with 26 examples, showing a high chemoselectivity of bromides vs chlorides.

Synthesis of ortho-Methylated Benzamides via Palladium-Catalyzed Denitrogenative Cross-Coupling Reaction of [1,2,3]-Benzotriazin-4(3H)-ones with DABAL-Me3

We herein developed a palladium-catalyzed reaction of [1,2,3]-benzotriazin-4(3H)-ones with DABAL-Me₃ [bis(trimethylaluminum)-1,4-diazabicyclo[2.2.2]octane adduct], a cheap, stable, and solid organoaluminum reagent. In the presence of Pd(OAc)₂/XantPhos as a commercially available catalyst, [1,2,3]-benzotriazin-4(3H)-ones underwent denitrogenative coupling with DABAL-Me₃ to afford a wide array of N-aryl amides derived from ortho-methylated carboxylic acids. Under the same catalytic conditions, ortho-ethylation of [1,2,3]-benzotriazin-4(3H)-ones could also be achieved by using triethylaluminum.

Convenient Synthesis of Salicylanilide Sulfonates from 1,2,3-Benzotriazin-4(3H)-ones and Organosulfonic Acids via Denitrogenative Cross-Coupling

An efficient and straightforward approach to synthesize salicylanilide aryl and alkyl sulfonates from 1,2,3-benzotriazin-4(3H)-ones and organosulfonic acids is described. This protocol is operationally simple and scalable, exhibits a broad substrate scope with high functional group tolerance, and affords the desired products in good to high yield. Application of the reaction is also demonstrated by converting the desired product to synthetically useful salicylamides in high yields.

Nickel-Catalyzed Cross-Electrophile Coupling of 1,2,3-Benzotriazin-4(3H)-ones with Aryl Bromides

The nickel-catalyzed cross-electrophile coupling of 1,2,3-benzotriazin-4(3H)-ones with aryl bromides to generate a diverse array of ortho-arylated benzamide derivatives has been developed. The reaction displayed good functional group tolerance with Zn as the reductant. The key to this transformation is the ring opening of benzotriazinones, which undergo a denitrogenative process to obtain various benzamide derivatives (29 examples, 42-93% yield). The scalability of this transformation was demonstrated.

Assembly of Benzo[c][1,2]dithiol-3-ones via Acid-Promoted Denitrogenative Transannulation of Benzotriazinones

An expedient synthesis of benzo[c][1,2]dithiol-3-ones via metal-free denitrogenative transannulation of benzotriazinones is developed, which represents the first example of acid-mediated heteroannulation of benzotriazinones. This newly discovered reactivity of benzotriazinones enables the streamline synthesis of diverse benzo[c][1,2]dithiol-3-ones in decent yields by using sodium sulfide as the sulfur source under simple reaction conditions.

Nickel-Catalyzed, Manganese-Assisted Denitrogenative Cross-Electrophile-Coupling of Benzotriazinones with Alkyl Halides for ortho-Alkylated Benzamides

A nickel-catalyzed denitrogenative cross-electrophile-coupling of benzotriazinones with unactivated alkyl halides (X = Cl, Br, I) in the presence of manganese powder as a reductant has been developed. The reaction furnishes ortho-alkylated secondary benzamides in modest to good yields under mild conditions. The scope of the reaction is demonstrated with 25 examples, showing good tolerance of steric hindrance and common functional groups, thus providing an efficient protocol to ortho-alkylated benzamide derivatives without the use of preprepared organometallic reagents.

Trifluoroacetic Acid-Mediated Denitrogenative ortho-Hydroxylation of 1,2,3-Benzotriazin-4(3H)-ones: A Metal-Free Approach

An efficient trifluoroacetic acid-mediated denitrogenative hydroxylation of 1,2,3-benzotriazin-4(3H)-ones is described. This metal-free approach is compatible with a wide range of 1,2,3-benzotriazin-4(3H)-ones, affording ortho-hydroxylated benzamides in good to high yields with a short reaction time. The reaction is believed to proceed via a benzene diazonium intermediate. The synthetic utility of the reaction was successfully demonstrated by the preparation of an antimicrobial drug, Riparin C, and benzoxazine-2,4(3H)-diones in good yields.

Visible-Light-Promoted Denitrogenative Ortho-selenylation Reaction of benzotriazinones: Synthesis of ortho-selenylated Benzamides, Ebselen Analogs

A visible-light-promoted regioselective denitrogenative cross-coupling between benzotriazinones and selenosulfonates is reported. This protocol allows for the convenient synthesis of ortho-selenylated benzamides in good yields from readily available starting materials under...

One-pot synthesis of N-substituted benzannulated triazoles via stable arene diazonium salts

A mild and effective one-pot synthesis of 1,2,3-benzotriazin-4(3H)-ones and benzothiatriazine-1,1(2H)-dioxide analogues has been developed. The method involves the diazotisation and subsequent cyclisation of 2-aminobenzamides and 2-aminobenzenesulfonamides via stable diazonium salts, prepared using a polymer-supported nitrite reagent and p-tosic acid. The transformation was compatible with a wide range of aryl functional groups and amide/sulfonamide-substituents and was used for the synthesis of pharmaceutically important targets. The synthetic utility of the one-pot diazotisaton-cyclisation process was further demonstrated with the preparation of an α-amino acid containing 1,2,3-benzotriazin-4(3H)-one.

Synthesis of ortho-arylated and alkenylated benzamides by palladium-catalyzed denitrogenative cross-coupling reactions of 1,2,3-benzotriazin-4(3H)-ones with organoboronic acids

An efficient palladium-catalyzed denitrogenative cross-coupling reaction of 1,2,3-benzotriazin-4(3H)-ones with organoboronic acids is described. The reaction affords various ortho-aryl and alkenylated benzamides in good to high yields.

Potassium tert-butoxide mediated aerobic hydroxylation of arylboronic acids: an application towards the synthesis of (E)-phenoxy acrylates

The first example of potassium tert-butoxide mediated aerobic hydroxylation of arylboronic acids affording phenols is described.