Experimental and theoretical study of the acylation reaction of aminopyrazoles with aryl and methoxymethyl substituents

Abstract

As a result of the chain of transformations from 1,3-butanedione with aryl and methoxy substituents through nitrosation and cyclization with hydrazine, the corresponding nitrosopyrazoles and aminopyrazoles were synthesized. According to this scheme, eight new previously unknown compounds were obtained. Their structures were established by the methods of IR, UV, 1 H NMR, 13 C NMR spectroscopy and mass spectrometry. DFT method of quantum-chemical calculations showed that obtained aminopyrazoles can exist as two tautomers; it was also confirmed by NMR 1 H spectroscopy data. In the case of acylation, an isomer is formed, where aryl substituent takes place in the fifth, rather than in the third position of the pyrazole ring, as shown by the DFT calculations.

Continuous Flow Synthesis of Methyl Oximino Acetoacetate: Accessing Greener Purification Methods with Inline Liquid–Liquid Extraction and Membrane Separation Technology

“…During the development of a continuous procedure for the generation and inline purification of methyl oximino acetoacetate ( 2 ) from methyl acetoacetate ( 1 ) by oximation with in situ generated nitrous acid (Scheme ), we encountered that extraction of 2 into an organic solvent was a challenging task. Optimization of a scalable procedure for the preparation of 2 was of special interest, as this compound is a key building-block for the synthesis of several heterocycles, including imidazoles, − (and their corresponding oxides), − pyrazines, , pyrazoles, and others. − Nitrous acid was generated under acidic conditions by mixing AcOH with aqueous sodium nitrite and reacted with 1 . The typical batch extractions described in the literature utilize large amounts of organic solvent to compensate for the solubility of 2 in both phases.…”