Silver(I)-Promoted ipso-Nitration of Carboxylic Acids by Nitronium Tetrafluoroborate

Abstract

A novel and efficient method for the regioselective nitration of a series of aliphatic and aromatic carboxylic acids to their corresponding nitro compounds using nitronium tetrafluoroborate and silver carbonate in dimethylacetamide has been described. This transformation is believed to proceed via the alkyl-silver or aryl-silver intermediate, which subsequently reacts with the nitronium ion to form nitro substances. Mild reaction conditions, tolerant of a broad range of functional groups, and formation of only the ipso-nitrated products are the key features of this methodology when compared to known methods for syntheses of nitroalkyls and nitroarenes.

Decarboxylation‐Initiated Intermolecular Carbon‐Heteroatom Bond Formation

“…Decarboxylative nitration of carboxylic acids was presented in 2015 by Natarajan and co‐workers (Scheme 65). [333] The transformation is promoted by Ag 2 CO 3 with nitronium tetrafluoroborate (NO 2 BF 4 ) as an electrophilic nitrating reagent and is generally applicable to both (hetero)aromatic and aliphatic acids. Its synthetic utility was demonstrated by the synthesis of two drugs, fexinidazole and nitazoxanide, in good yields.…”

Ipso Nitration of 2‐Halothiophenes with Silver Nitrate

“…Saito and Koizumi reported on the copper‐catalyzed nitration of iodoarene derivatives, and Buchwald and Fors reported on the nitration of aryl chlorides, triflates, and nonaflates using a palladium catalyst. Subsequent to that report, several alternate metal‐catalyzed nitration systems were also reported –…”

Palladium-Catalyzed Direct o-Nitrification of Azobenzenes with Co(NO3)2·6H2O via C-H Activation

“…But these reaction conditions are harsh and have many serious problems of environmental pollution. Hence, more attention have been attracted in developing methods to perform nitration under milder conditions, for example, the iso-nitration of many arylboronic acids, [2] carboxylic acids, [3] aryl halides and pseudohalides. [4] In the past decade, C-H functionalization has emerged as a powerful tool for regioselective formation of C-C, C-O, C-N and Chalogen bonds.…”

“…Ag-NO 3 [5] and t-butyl nitrite [6] are good nitro source but the price is high. Recently, many significant progress has been made in nitrification reagents such as NO 2 , [7] bismuth nitrate [8] and Fe(NO 3 ) 3 •9H 2 O. [9] Azobenzenes have attracted much interest due to their applications as pharmaceuticals, [10] liquid crystals, [11] molecular switches, [12] femtosecond fluorescence.…”