The first example of functionalization of mesoionic 3‐R‐1,2,3,4‐oxatriazol‐5‐ones and 3‐substituted‐1,2,3,4‐oxatriazol‐5‐imines (azasydnones and azasydnonimines, respectively) by the electrophilic reaction without destruction of the oxatriazole ring is reported. Nitration of a range of aryl derivatives bearing various electron donating and withdrawing substituents at the ortho‐, meta‐ and para‐positions using HNO3/H2SO4 mixtures has been assessed in order to develop an approach for the synthesis of corresponding nitroaryl derivatives. Whereas nitration occurs meta to the azasydnone ring, the regioselectivity of the electrophilic substitution can be affected by the nature of the substituent attached to the aryl ring, and a variety of polyfunctionalized derivatives can be readily accessed by using this methodology, which may have applications in the target‐oriented synthesis. The reactivity, synthesis, and structure of the mesoionic 3‐substituted‐1,2,3,4‐oxatriazole derivatives described here provide interesting new information on this known but poorly understood heterocycle.
[reaction: see text] The reduction of benzo-1,2,3,4-tetrazine 1,3-dioxides (BTDOs) 1 with Na(2)S(2)O(4) or SnCl(2) is suggested to proceed via intermediate N-nitrosobenzotriazoles 3 to afford benzotriazoles 2. The (15)N-labeling experiments exhibit that the N-3 atom of the tetrazine ring is incorporated into the nitroso group of 3 that is ultimately released into solution. It is possible that the biological activity of BTDOs is due to their ability to release nitrosating species, i.e., N-nitrosotriazol 3 or HNO(2), in the course of reduction.
A practical nickel‐catalyzed protocol for the synthesis of sterically hindered 9‐arylacridines via Negishi type cross‐coupling was developed. The method enables a convenient approach to a set of active acridine photocatalysts starting from commercially available 9‐chloroacridine, inexpensive catalyst [NiCl2(Ph3P)2], and organozinc reagent with no need for additional ligands and precious metals. The synthetic protocol could be readily performed on a gram scale. The photocatalytic efficiency of obtained acridines was tested in decarboxylative thiolation and amination reactions. Structures of 19 acridines were studied by X‐ray analysis, which allowed to propose a steric descriptor relevant to the catalytic activity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.