Order versus disorder in two isomorphous pyrazolone-substituted diethyl propane-dioates prepared using a three-component one-pot reaction under solvent-free conditions.

Tharangini K Shreekanth,Hemmige S Yathirajan,Christopher Glidewell,Balakrishna Kalluraya,Sabine Foro

doi:10.1107/s2056989020011676

Abstract

Two new substituted propane-dioate esters have been synthesized using a three-component solvent-free thermal reaction between diethyl propane-dioate (diethyl malonate), 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde and an aryl azide, forming two new C-C bonds in a single step. The products diethyl (RS)-2-[(4-bromo-phen-yl)(5-methyl-3-oxo-2-phenyl-2,3-di-hydro-1H-pyrazol-4-yl)meth-yl]propane-dioate, C24H25BrN2O5 (I), and diethyl (RS)-2-[(4-chloro-phen-yl)(5-methyl-3-oxo-2-phenyl-2,3-di-hydro-1H-pyrazol-4-yl)meth-yl]propane-dioate, C24H25ClN2O5 (II), are isomorphous, with Z' = 2 in space group P21/n. The two independent mol-ecules in compound (I) are both fully ordered, while each of the independent mol-ecules in compound (II) is disordered, but in different ways. In one mol-ecule of (II), the N-phenyl ring is disordered over two sets of atomic sites having occupancies 0.635 (10) and 0.365 (10), and in the other mol-ecule the ester function is disordered over two sets of atomic sites having occupancies 0.690 (5) and 0.310 (5). In both structures, the two independent mol-ecules adopt different conformations and, in each structure, the mol-ecules are linked into complex sheets by a combination of N-H⋯O, C-H⋯O and C-H⋯π(arene) hydrogen bonds. Comparisons are made with some related structures.

Highlights

Two new substituted propanedioate esters have been synthesized using a threecomponent solvent-free thermal reaction between diethyl propanedioate, 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde and an aryl azide, forming two new C—C bonds in a single step
In one molecule of (II), the N-phenyl ring is disordered over two sets of atomic sites having occupancies 0.635 (10) and 0.365 (10), and in the other molecule the ester function is disordered over two sets of atomic sites having occupancies 0.690 (5) and 0.310 (5)
In a continuation of a broadly based study of the synthesis and structures of novel pyrazole derivatives (Asma et al, 2018; Kiran Kumar et al, 2020; Shaibah et al, 2020a,b), we have investigated a three-component reaction between diethylpropanedioate, 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde and some aryl azides

Summary

Chemical context

Pyrazoles exhibit a very wide range of pharmacological and other biological activities, which have recently been extensively reviewed (Ansari et al, 2017; Karrouchi et al, 2018). Our expectation was that the methylene group of the ester component would undergo a condensation reaction with the carbaldehyde function to provide a new electron-deficient alkene system, which would undergo a 1,3-dipolar cycloaddition with the aryl azide to provide pyrazole-substituted 1,2,3-triazoles. The yields were fairly low, in the range 35–40%, and the course of the reaction is unclear: the by-products must include HCl and HN3, and the H atoms in these by-products may well arise from thermal degradation of one or more of the reactants, the ester component. We report the synthesis of compounds (I) and (II), the reaction sequence for which is summarized in Fig. 5, and their molecular and supramolecular structures

Structural commentary

Database survey

Supramolecular features

Synthesis and crystallization

Refinement

Funding information