RESUMO
Carboxylic acids and thiols are basic chemical compounds with diverse utility and widespread reactivity. However, the direct conversion of unprotected acids to thiols is hampered due to a fundamental problem - free thiols are incompatible with the alkyl radicals formed on decarboxylation of carboxylic acids. Herein, we describe a concept for the direct photocatalytic thiolation of unprotected acids allowing unprotected thiols and their derivatives to be obtained. The method is based on the application of a thionocarbonate reagent featuring the N-O bond. The reagent serves both for the rapid trapping of alkyl radicals and for the facile regeneration of the acridine-type photocatalyst.
RESUMO
A reaction of aromatic halides bearing electron-withdrawing groups with tertiary amines in the presence of an iridium catalyst under blue light irradiation is described. Products of the aromatic substitution of the halide by the dialkylamino fragment are obtained. The interaction of aryl radicals with tertiary amines to generate zwitterionic radical species is believed to be the key factor responsible for the reaction efficiency.
RESUMO
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 /H2 SO4 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.
RESUMO
[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.
