Synthesis of C2-Symmetrical Bis-(β-Enamino-Pyran-2,4-dione) Derivative Linked via 1,6-Hexylene Spacer: X-ray Crystal Structures, Hishfeld Studies and DFT Calculations of Mono- and Bis-(Pyran-2,4-diones) Derivatives

Ahmed T A Boraei,Assem Barakat,Matti Haukka,Abdullah Mohammed Al-Majid,Saied M Soliman,Ahmed A M Sarhan

doi:10.3390/sym13091646

Abstract

The synthesis of C2-symmetrical bis(β-enamino-pyran-2,4-dione) derivative 3 connected via 1,6-hexylene linker was reported for the first time. X-ray structures and Hirshfeld studies of the new bis- β-enamino-pyran-2,4-dione derivative 3 along with two structurally related pyran-2,4-dione derivatives 2a,b were discussed. A comparative analysis of the different intermolecular contacts affecting the crystal stability was presented. Generally, the H…H, O…H, and H…C interactions are common in all compounds and are considered the most abundant contacts. In addition, DFT calculations were used to compute the electronic properties as well as the 1H and 13C NMR spectra of the studied systems. All compounds (except 3) are polar where 2a (3.540 Debye) has a higher dipole moment than 2b (2.110 Debye). The NMR chemical shifts were calculated and excellent correlations between the calculated and experimental data were obtained (R2 = 0.93–0.94).

Highlights

Pyrone and its analogs have been in the focus of organic chemists due to their wide range of interesting chemical properties, in addition to many biological and therapeutic applications [1,2,3]
Pyrone scaffold and related analogs have multi-functional groups such as enone, ester group, and conjugated diene which can serve as versatile building blocks for the synthesis of numerous target molecules [3]
Chemical shifts were represented in δ and coupling constants are given in Hz

Summary

Introduction

Pyrone and its analogs have been in the focus of organic chemists due to their wide range of interesting chemical properties, in addition to many biological and therapeutic applications [1,2,3]. They are considered as good synthons in a number of synthetic transformations, especially the ones leading to natural products heterocyclic systems isolated from fungi, bacteria, insects, animals, plants, and marine organisms that possess a wide range of pharmaceutical actions such as phytotoxic, neurotoxic, cytotoxic, antifungal, and anti-biotic activities [4]. Some important investigations have been carried out and reported recently on the synthesis and spectroscopic behavior of pyrone scaffold [22,23,24,25]

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