Heterocycle-to-Heterocycle Route to Quinoline-4-amines: Reductive Heterocyclization of 3-(2-Nitrophenyl)isoxazoles (original) (raw)
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Concise Synthesis of 2-Amino-4(3 H )-quinazolinones from Simple (Hetero)aromatic Amines
The Journal of Organic Chemistry, 2008
A novel and simple method of preparation of 2-alkylaminoquinazolin-4-ones with fused heteroaromatic rings from easily accessible (hetero)aromatic amines is described. The method is very efficient, and the 2-alkylaminoquinazolinone derivatives are obtained in three steps without chromatographic purification. The key step is the ring closure of the N-protected guanidine intermediates by intramolecular Friedel-Craft's type substitution.
JOURNAL OF EDUCATION AND SCIENCE, 2021
In this research new compounds containing quinazolin-4(3H)-one nucleus linked to heterocyclic moieties were synthesized using ethyl (4'-oxoquinazolin-3'-yl) acetate (2) as a synthon. This compound was synthesized via 4-quinazolinone's (1) reaction with ethyl chloroacetate in the existence of K2CO3 as a base and acetone as a solvent. The ethyl α-(4'-oxoquinazolin-3'-yl) acetate (2) was converted to the corresponding hydrazide through its reaction with hydrazine hydrate (85 %). Compound (3) was reacted with two of acyl chlorides to synthesize the diacyl hydrazine compounds (4,5). The compound (5) was cyclized to the corresponding 1,3,4-oxadiazole (6) in presence of phosphorous oxychloride. The formyl derivative (7) of the hydrazide (3) was synthesized via its reaction with formic acid and consequently cyclized by phosphorous oxychloride to the corresponding 1,3,4-oxadiazole (8). The hydrazide (3) was also converted to the thiosemicarbazide derivative (9) by its reaction with ammonium thiocyanate under acidic conditions. Whereas other substituted thiosemicarbazide derivatives (10-12) were synthesized by the reaction of hydrazide (3) with organic isothiocyanate compounds. The resultant compounds (11, 12) were cyclized under basic conditions (4% sodium hydroxide solution) to give 1,3,4-triazole-2-thiole derivatives (13,14), whereas the cyclization of compounds (10-12) was performed under the acidic medium (conc. H2SO4) to give 2substituted amino-1,3,4-thiadiazoles (15-17). On the other side, the hydrazide's (3) reaction with isocyanate compounds affords the semicarbazide compounds (18,19). These compounds were cyclized under the basic condition to afford 1,3,4-triazol-2-ol compounds (20,21). The structures of the synthesized compounds were corroborated depending on the physical and spectral data.
Synthesis and oxidative cyclization of 7-amino-3-R-4,6-dinitrobenzo[d]isoxazoles
Russian Chemical Bulletin, 2009
A method was developed for the selective amination of 3 R 4,6 dinitrobenzo[d]isoxazoles at position 7 via the oxidative nucleophilic substitution of hydrogen. The resulting nitroamines were used to synthesize representatives of the previously unknown tricyclic heteroaromatic system, viz., isoxazolo[5,4 e]benzofuroxan.
A novel approach for the one-pot synthesis of linear and angular fused quinazolinones
Tetrahedron Letters, 2011
Cs 2 CO 3 Linear and angular annulated quinazolinones a b s t r a c t A convenient and inexpensive one step methodology has been developed for the synthesis of linear and angular fused quinazolinones. The protocol, which uses amino heterocycles and o-bromo benzyl/naphthyl bromides as reactants, CuI as catalyst, Cs 2 CO 3 as base, L-proline as ligand, and DMF as solvent, proceeds via nucleophilic aromatic substitution of the N-heteroaromatic cationic intermediate followed by in situ aerial oxidation at the benzylic position to the quinazolinone scaffold.
New Opportunities for the Synthesis of Quinoxaline-Substituted Heterocyclic and Aryl Moieties
Pharmaceutical Chemistry Journal, 2013
DMSO solution in the presence of acid to form mono-substituted products IIa-c. Heating I with resorcinol in EtOH in the presence of acid gave resorcinol derivative IId. 6.7-Difluoroquinoxaline in the presence of base reacted with 3-methyl-1-phenylmethylpyrazol-5-one to form dipyrazolylmethane III and tetrapyrazolylethane derivative IV. Heating products IIa-c with N-methylpiperazine produced 7-methylpiperazine derivatives Va-c of 2-substituted quinoxalines.