Benzoic acids 4-fluoro-3-nitro

Benzoic acid, fluoro subs, 335 Benzoic acid, hydroxy subs, 206 Benzoic acid, nitro subs, 83 Benzoin, 464... 

Fluoro and 3- or 5-nitro-2-chloropyridine A-oxides may be converted to the corresponding l-benzoyloxy-2-pyridones by reaction with benzoic acid alone. 

Intramolecular cyclisation of the azides (79) by refluxing in toluene has produced the [ 1,2,3]triazolo[ 1,5-u][ 1,4]diazepines (80) <95S647>. Removal of the Boc protecting group in the benzodiazepine derivative (81), prepared in three steps from 2-fluoro-5-nitro-benzoic acid, results in ring expansion to (82) via a Smiles rearrangement <95SL539>. 

A recently reported synthesis sequence [152] starts from MeOPEG-bound 4-fluoro-3-nitro-benzoic acid. After the nucleophilic aromatic substitution of the fluorine with piperazine, homopiperazine and 4-aminomethyl-piperidine (only the secondary amino group reacted) the remaining free amino function was acylated or sulfonated. 

A range of simple analogs of benzoic acid and phenylalanine, easily obtainable from standard chemical suppliers, were chosen as substrates. These included a large number of hydroxy- and dihydroxybenzoic acids, aminoben-zoic acids, nitrobenzoic acids, fluoro-, difluoro-, trifluoro-, tetrafluoro- and pentafluorobenzoic acids, chlorobenzoic acids, iodobenzoic acids, and methoxybenzoic acids. A number of structures other than those with a six-mem-bered aromatic ring were also tried, including pyridinecarboxaldehydes, alicy-clic carboxylic acids, naphthalenecarboxylic acids, furancarboxylic acids, thiophenecarboxylic acids, nitro-, bromo-, and chlorothiophenecarboxyhc acids. 

In order to investigate the further application of immobilized 4-fluoro-3-nitro benzoic acid synthon, we expanded our methodology to prepare 1,2-disubstituted benzimidazoles 23-25. Figure 11 shows our detailed efforts toward the preparation of a benzimidazole library. To achieve this goal, one pot cyclization of PEG-bound diamine 12 with trimethylorthoformate in TEA/... 

In order to demonstrate the versatility of the immobilized 4-fluoro-3-nitro benzoic acid scaffold 10, we also synthesized benzopiperazinones derivatives. The building block used for the synthesis of benzopiperazinones is shown in Fig. 14. Complete acylation of 12 at the secondary aniline site was achieved by a reaction with chloroacetyl chloride in the presence of triethyl amine. Finally, one pot intramolecular cyclization of 25 and cleavage was done with NaOMe/ MeOH at room temperature. According to the thin layer chromatography analy-... 

Collect the precipitate on a glass funnel and thoroughly wash with diethyl ether several times to remove unreacted DCC, DMAP, and 4-fluoro-3-nitro benzoic acid. 

Schemesl2 and 13) [43-53]. Privileged structures of IL-immobilized diamines 97 and 99 were synthesized from 4-fluoro-3-nitrobenzoic acid and 4-(bromomethyl)-3-nitrobenzoic acid, respectively over three steps (Scheme 14). The ionic liquid 3-hydroxyethyl (l-methylinidazolium)-tetrafluoroborate ([hydemim][BF4]) 1 was selected as appropriate IL support in all multistep transformations. Benzoic acid 94 coupled with IL1 through esterification followed by ipso-fluoro and bromo displacement by primary amines and subsequent nitro reduction afforded ort/fo-phenylenediamines 97 and 99. 

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