Substituent-modulated conformation and supramolecular assembly of tetronamides
Nenhuma Miniatura disponível
Data
2016
Título da Revista
ISSN da Revista
Título de Volume
Editor
Resumo
The crystal structures of nine compounds (1–9) bearing the 4-aminofuran-2(5H)-one scaffold (commonly known as tetronamide, C4H5NO2) and two decorating aromatic/heteroaromatic moieties with two stereocenters have been determined. Tetronamides bearing at the 5-position a phenyl moiety (1 and 2, 3-chloro derivatives with either a 4-p-tolylamino or 4-p-bromophenylamino substituent), an o-bromopyridyl moiety (3, a 3-bromo-4-p-tolylamino derivative), or an o-tolyl moiety (4, a 3-bromo-4-p-tolylamino derivative) adopt a U-shaped conformation. This conformation is stabilized by an intramolecular contact involving either the phenyl o-CH moiety (1 and 2) or the substituent at the ortho position (3 and 4) and the π system of the N-phenyl ring. The other five tetronamides (5–9) are not present with such an intramolecular contact. In fact, these last five compounds are not U-shaped and feature the presence at the 5-position of a p-biphenyl moiety (5 and 7, 3-bromo-4-p-tolylamino diastereomers differing as 5R and 5S), a p-methoxyphenyl moiety (6, a 3-chloro-4-p-bromophenylamino derivative), or a 5-chlorofuran-2-yl moiety (8 and 9, 3-chloro-4-p-tolylamino diastereomers differing as 5R and 5S). Crystal structures of a 5,5-disubstituted tetronamide bearing m-nitrophenyl moieties (10) and a parent tetronamide without a substituent at the 5-position (11d) reinforce the conformational trend found in 1–9. Furthermore, OH···O centrosymmetric dimers are formed only in the crystal structures of the U-shaped tetronamides. Chain motifs assembled through OH···O and NH···O hydrogen bonds are preferred in the line-shaped tetronamides. Furthermore, the conformer energies were calculated in both the gas and solution phases (B3LYP/6-31G*). The lowest-energy conformations feature an intramolecular N–H···O hydrogen bond as in the crystal structure of 7. In the U-shaped tetronamides, the crystal structure conformations are similar to the third or fourth energetically ranked stable calculated conformer. Therefore, it is concluded that the substitution pattern in the U-shaped tetronamides allows for accessible secondary minimum-energy conformations that are easily adopted in the crystal structure as a result of their compatibility with the robust centrosymmetric O–H···O dimer formation.
Descrição
Palavras-chave
Citação
KARAK, Milandip et al. Substituent-modulated conformation and supramolecular assembly of tetronamides. Crystal Growth & Design, Washington, v. 16, n. 10, p. 5798-5810, 2016. DOI: 10.1021/acs.cgd.6b00881. Disponível em: https://pubs.acs.org/doi/10.1021/acs.cgd.6b00881. Acesso em: 28 nov. 2023.