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Mild Nitration of Pyrazolin‐5‐ones by a Combination of Fe(NO 3 ) 3 and NaNO 2 : Discovery of a New Readily Available Class of Fungicides, 4‐Nitropyrazolin‐5‐ones
Author(s) -
Krylov Igor B.,
Budnikov Alexander S.,
Lopat'eva Elena R.,
Nikishin Gennady I.,
Terent'ev Alexander O.
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201806172
Subject(s) - nitration , chemistry , fungicide , nano , nitrite , reagent , triadimefon , medicinal chemistry , combinatorial chemistry , organic chemistry , materials science , horticulture , nitrate , composite material , biology
4‐Nitropyrazolin‐5‐ones have been synthesized by the nitration of pyrazolin‐5‐ones at room temperature by employing the Fe(NO 3 ) 3 /NaNO 2 system. The method demonstrated selectivity towards the 4‐position of pyrazolin‐5‐ones even in the presence of NPh and allyl substituents, which are sensitive to nitration. It was shown that other systems containing Fe III and nitrites, namely Fe(NO 3 ) 3 / t BuONO, Fe(ClO 4 ) 3 /NaNO 2 , and Fe(ClO 4 ) 3 / t BuONO, were also effective. Presumably, Fe III oxidizes the nitrite (NaNO 2 or t BuONO) to form the NO 2 free radical, which serves as the nitrating agent for pyrazolin‐5‐ones. The synthesized 4‐nitropyrazolin‐5‐ones were discovered to be a new class of fungicides. Their in vitro activities against phytopathogenic fungi were found comparable or even superior to those of commercial fungicides (fluconazole, clotrimazole, triadimefon, and kresoxim‐methyl). These results represent a promising starting point for the development of a new type of plant protection agents that can be easily synthesized from widely available reagents.