A green synthesis of nitrones from diamino glyoxime using aldehydes and ketones

Abstract

The reaction of diaminoglyoxime with aldehyde and ketone derivatives in the presence of p-toluene sulphonic acid in H 2 O-MeOH mixture at room temperature afforded nitrone derivatives in high yields within 10-140 min. The applicability of ketones in this reaction for the preparation of novel nitrones has been verified. The effect of the temperature on the stability of the structural isomers of the products has been studied by NMR as well. The results showed that, at high temperatures only one product could be observed. The nature of solvent and catalyst were evaluated and found that the strong acids H 2 SO 4 and CF 3 SO 3 H in protic solvent CH 3 OH work well while neither CH 3 SO 3 H in protic solvent nor p-toluene sulphonic acid in aprotic solvents toluene and THF perform the same reactions.

Diaminoglyoxime as a versatile reagent in the synthesis of bis(1,2,4-oxadiazoles), 1,2,4-oxadiazolyl-quinazolines and 1,2,4-oxadiazolyl-benzothiazinones

“…It was assumed that nitrone 4 [2], produced from the reaction of DAG 1 and ketone 2, can undergo nucleophilic substituted and intermolecular cyclocondensation reactions with methyl 2-aminobenzoate 3 to generate benzodiazepine I. This assumption was made based on a report describing the capability of amidoximes and DAG to produce quinazolinone derivatives [5].…”

“…The chemistry of DAG in the synthesis of biologically active compounds has not been developed, yet. There are limited reports in the literature in which DAG was used in the synthesis of nitrones [2], bis(1,2,4-oxadiazole) [3,4] and quinazolines [5].…”

“…In this work, as a part of our current studies in the chemistry of DAG [2,5] and synthesis of benzodiazepines [39-41], a novel approach was designed for the synthesis of a new class of benzodiazepine derivatives I via a one-pot sequential multi-component condensation reaction of diaminoglyoxime (DAG) (1), ketone (2) and methyl 2-aminobenzoate (3) in acetic acid as the catalyst and solvent at 100 • C. However, instead of obtaining desired product I, the reaction proceeded via an unexpected route affording a new class of bis(1,2,4-oxadiazoles) (5) in good yields (Scheme 1).…”

ZnO NPs: an efficient and reusable nanocatalyst for the synthesis of nitrones from DAG using H2O as a solvent at room-temperature

“…The chemistry of DAG in the synthesis of biologically active compounds has not been developed, yet. There are limited reports in the literature in which DAG was used in the synthesis of nitrones [3], bis(1,2,4-oxadiazole) [4,5] and quinazolines [6,7].…”

“…To the best of our knowledge, there are two known cases in the literature reported in which DAGacted as an amine source for the synthesis of nitrones [3,43]. Herein, we wish to report the modification of the previously published methodology for the preparation of nitrones from DAG 1 with aldehydes and ketones.…”