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

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.

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.

Rotamer-Controlled Dual Emissive α-Amino Acids

The synthesis and photoluminescent properties of novel α-amino acids are described in which the biaryl benzotriazinone-containing chromophores were found to display dual emission fluorescence via locally excited (LE) and twisted intramolecular charge transfer (TICT) states. The intensity of each emission band could be controlled by the electronics and position of the substituents, and this led to the design of a 2-methoxyphenyl analogue that, due to twisting, displayed bright TICT fluorescence, solvatochromism, and pH sensitivity.

Photochemical Aminochlorination of Alkenes without the Use of an External Catalyst

The niche field of photochemistry offers opportunities that are not found in "traditional" ground state chemical pathways. Aminochlorinated derivatives are an interesting family of 1,2-difunctionalised compounds that provide access to a variety of natural products and pharmaceutical active substances. A practical, catalyst-free chloroamination protocol is described herein, providing access to intermediates of great importance, utilising mild and photochemical reaction conditions (370 nm), where N-chlorosulfonamides are used as both nitrogen and chlorine sources. A wide variety of olefins, decorated with a plethora of functional groups, was tested providing excellent results (28 examples, 18-88 % yield). Mechanistic studies (UV-Vis, control experiments and quantum yield measurement) were also performed.

Catalytic Aerobic N-Nitrosation by Secondary Nitroalkanes in Water: A Tandem Diazotization of Aryl Amines and Azo Coupling

Secondary nitroalkanes underwent oxygen-mediated nitro-nitrite isomerization, serving as versatile N-nitrosating agents under aerobic conditions. To capitalize on the newly discovered aerobic nitro-nitrite isomerization phenomenon, a phase-transfer catalysis system employing KSeCN and TBAI was developed, in which the tandem diazotization and azo coupling with nitroalkanes as well as N-nitrosation of amines were accomplished. The current tandem diazotization and azo coupling strategy provides a facile synthesis of areneazo-2-(2-nitro)propane derivatives, a safe synthetic alternative to aryl diazonium salts.