Tandem of nucleophilic substitution of hydrogen and cyclocondensation with participation of nitro group in the synthesis of fluorine-containing 3-amino-1,2,4-benzotriazines

Generation of 1,2-Difluorobenzene via a Photochemical Fluorodediazoniation Step in a Continuous Flow Mode

“…It has to be noted that cooling was not applied, which resulted in a reactor temperature of 27−30 °C. The higher temperature did not alter the 19 F NMR purity profile, though. No further optimizations were conducted with this light source, and we moved directly to a 365 nm LED that has a higher photon output (150 W input power and 60 W output power, Figure 3c; see also the Supporting Information) than that of the standard LED.…”

“…Initial experiments were performed with tBuONO as the nitrosating agent since this protocol has already been successfully reported for a fully continuous Balz−Schiemann reaction by Naber and coworkers. 34 Gas bubbles were observed within the first 20 min (see Figure S1), most probably the result of the extrusion of N 2 , and the formation of side products was detected by 19 F NMR (see Figure S2). The one-pot protocol described by Saint-Jalmes and Garel 25 using tBuONO and BF 3 •Et 2 O was also not suitable since the diazonium BF 4 salt precipitated from the reaction mixture.…”

“…Next, the standard 365 nm LED (62 W input power and 16 W output power, Figure 3b) was tested. Compared to the Hg lamp, an inferior reaction performance was achieved: at a concentration of 0.4 M of 2 (4.1 mmol of 2 and 90 equiv of HF/pyridine) and a residence time of 50 min, product 3 was obtained in only 77% conversion by 19 F NMR (entry 10, Table 1). It has to be noted that cooling was not applied, which resulted in a reactor temperature of 27−30 °C.…”

Synthesis of fluorine-containing quinoline-2,3-dicarboxylates from products of vicarious nucleophilic substitution of hydrogen in 3-fluoronitroarenes

“…For our study, we chose 4 R 3 fluoronitrobenzenes 1a-c, which were synthesized by the reaction of 3,4 difluoronitroben zene with the corresponding alcohols or cycloalkyl amines. 21 Earlier, we have shown 22 that the vicarious nucleophilic substitution of hydrogen in nitroarenes 1a-c with chloromethyl phenyl sulfone proceeds selectively at the ortho position with respect to the nitro group to form 3 fluoro 4 R 6 phenylsulfonylmethylnitrobenzenes 2a-c in 60-70% yields (Scheme 1). It was found that the reactions of 3 fluoro 4 R 6 phenylsulfonylmethylnitrobenzenes 2a-c with α,β un saturated acid esters (dimethyl fumarate or diethyl maleate) in acetonitrile in the presence of an excess of K 2 CO 3 as the base and a catalytic amount of 18 crown 6 afforded mixtures of the following three products: dialkyl 6 R 7 fluoroquinoline 2,3 dicarboxylate N oxides (8a-c or 9a-c) (18-30%), dialkyl 6 R 7 phenylsulfonyl quinoline 2,3 dicarboxylate N oxides (10a-c or 11a-c) (35-40%), and dialkyl 6 R 7 fluoroquinoline 2,3 dicar boxylates (12a-c or 13a-c) (23-30%), which were sepa rated by preparative column chromatography.…”

SN H reactions of 3-fluoronitroarenes with chloromethyl sulfone as the method for the construction of 6-fluoro-3-sulfonylindoles

“…15 In the present work, a possibility of application of the S N H methodology in nitroarenes as the key step in the synthe sis of fluoro containing 3 sulfonylindoles was studied. It was found that the reaction of 4 R 3 fluoro nitrobenzenes 1b-f with chloromethyl phenyl sulfone, proceeding in DMSO in the presence of KOH at room temperature, leads to the selective substitution of the H(6) hydrogen atom in o position to nitro group and is finished by the formation of 4 R 3 fluoro 6 (phenylsulfonyl methyl)nitrobenzenes 2b-f in 60-71% yield ( Table 1).…”