Synthesis and Conformational Analysis of Sterically Congested (4R)-(−)-1-(2,4,6-Trimethylbenzenesulfonyl)-3-n-butyryl-4-tert-butyl-2-imidazolidinone: X-Ray Crystallography and Semiempirical Calculations

Ibrahim A Al-Swaidan,Amer M Alanazi,Adel S El-Azab,Alaa A.-M Abdel-Aziz

doi:10.1155/2014/173902

Ibrahim A Al-Swaidan, Amer M Alanazi + Show 2 more

Open Access

https://doi.org/10.1155/2014/173902

Copy DOI

Abstract

The crystal structure of (4R)-(−)-1-(2,4,6-trimethylbenzenesulfonyl)-3-n-butyryl-4-tert-butyl-2-imidazolidinone(3)was determined by single-crystal X-ray diffraction. Compound3crystallizes in triclinic system in space groupP1 (≠1). The crystal data area=10.62165 Å,b=16.5321 Å,c=8.95729 Å,∝=91.1936∘,β=93.8496∘,γ=88.0974∘,V=1568.22 Å3,Z=3,Dcalc=1.253 g/cm3,μCuKα=15.98 cm−1,F000=636.00,T=20.0°C, andR=0.037. The crystal structure confirmed the occurrence of three molecules of3A,3B, and3Cin which then-butyryl moiety adopted thes-transoidconformation. Crystal structure also revealed that the conformation of 2,4,6-trimethylbenzenesulfonyl groups was inanti-position relative totert-butyl group. The crystal packing showed that three molecules of compound3are stacked as a result of intermolecularπ-πinteractions between the phenyl ring of one molecule and the phenyl ring of the other molecule by approaching each other to an interplanar separation of 5.034 Å. Interestingly, these stacked molecules are also connected by intermolecularCH-πinteraction. The conformational analysis of thes-transoid 3A,3B, and3Cwas separately performed by molecular mechanic MM+ force field. Additionally, computational investigation using semiempirical AM1 and PM3 methods was performed to find a correlation between experimental and calculated geometrical parameters. The data obtained suggest that the structural data furnished by the AM1 method is in better agreement with those experimentally determined for the above compound. It has been found that the lowest energetic conformer computed gives approximate correspondence with experimental solid state data.

Highlights

The energy based conformational searching technique is a considerable computational request and is still an active area of research
We reported the synthesis and chiral application of 4-tertbutyl-2-imidazolidinone which were greatly enhanced by the occurrence of N-arylsulfonyl fragments [4]
The results show that atoms of the n-butyryl, and 2,4,6-trimethylphenylsulfonyl groups occupy different spatial positions relative to the plane of 2-imidazolidinone ring which may explain the existence of such three molecules in one unit cell

Summary

Introduction

The energy based conformational searching technique is a considerable computational request and is still an active area of research. When the property of interest is energy, the following methodology is indicated: full conformational search using molecular mechanics, followed by geometry optimization using semiempirical model for selected conformers, and single-point calculation using ab initio models for selected conformers [1]. Steric bulkiness of chiral 2-imidazolidinones [2] plays an effective role in greatly enhancing stereoselectivity, and so sterically congested chiral 2-imidazolidinones [3,4,5] represent promising auxiliaries for providing excellent diastereocontrol. We reported the synthesis and chiral application of 4-tertbutyl-2-imidazolidinone which were greatly enhanced by the occurrence of N-arylsulfonyl fragments [4]. More interestingly the structure of the arylsulfonyl-2-imidazolidinone such as 4-benzamido-3-methyl-1-tosyl-2-imidazolidinone and (S)-(+)-1-[1-(4-aminobenzoyl) indoline-5sulfonyl]-4-phenyl-4,5-dihydroimidazol-2-one has elucidat-

Objectives

Results

Conclusion