Understanding the conformational changes and molecular structure of furoyl thioureas upon substitution

Abstract

1-Acyl thioureas [RC(O)NHC(S)NRR] are shown to display conformational flexibility depending on the degree of substitution at the nitrogen atom. The conformational landscape and structural features for two closely related thioureas having R=2-furoyl have been studied. The un-substituted 2-furoyl thiourea (I) and its dimethyl analogue, i.e. 1-(2-furoyl)-3,3-dimethyl thiourea (II), have been synthesized and fully characterized by spectroscopic (FT-IR, H andC NMR) and elemental analysis. According to single crystal X-ray diffraction analysis, compounds I and II crystallize in the monoclinic space group P21/c. In the compound I, the trans-cis geometry of the almost planar thiourea unit is stabilized by intramolecular NH⋯OC hydrogen bond between the H atom of the cis thioamide and the carbonyl O atom. In compound II, however, the acyl thiourea group is non-planar, in good agreement with the potential energy curve computed at the B3LYP/6-31+G(d,p) level of approximation. Centrosymmetric dimers generated by intermolecular NH⋯SC hydrogen bond forming R(8) motif are present in the crystals. Intermolecular interactions have been rationalized in terms of topological partitions of the electron distributions and Hirshfeld surface analysis, which showed the occurrence of S⋯H, O⋯H and H⋯H contacts that display an important role to crystal packing stabilization of both thiourea derivatives.

The trans -[Ru(PPh 3 ) 2 ( N , N -dimethyl- N ′-thiophenylthioureato-k 2 O,S)(bipy)]PF 6 complex has pro-apoptotic effects on triple negative breast cancer cells and presents low toxicity in vivo

“…Detailed description of syntheses and characterization of related acylthioureas has been previously reported [12]. The identity of the products was confirmed by analysis of 1 H and 13 C NMR spectra in comparison to similar compounds previously reported in the literature [13][14][15].…”

An Intramolecular CAr–H•••O=C Hydrogen Bond and the Configuration of Rotenoids

“…The existence of non-classical C–H•••O H-bonds was confirmed by analysis of the total charge density method [40], and an intramolecular N–H•••O=C H-bond between the H atom of a cis thioamide and a carbonyl oxygen atom has been supported by single-crystal X-ray diffraction analysis, with a trans – cis geometry of the almost planar thiourea unit found stabilized by this H-bonding [41]. Recently, an intramolecular C Ar –H•••O=C H-bond has been reported, based on X-ray diffraction data [42], and the chemical shift of an intramolecular “non-classical” H-bonding C–H proton was found shifted downfield about 1 ppm [43].…”

Síntesis, estudios espectroscópicos, estructurales y conformacionales de nuevas especies de tioureas y guanidinas

“…En las tio-y seleno-ureas simétricamente di-sustituidas igualmente se observan enlaces de hidrógeno intermoleculares N-HO, C-HS/Se y C-HO, que favorecen patrones de repetición del tipo de cadenas supramoleculares orientadas a lo largo de ejes cristalográficos [55,56]. En algunas estructuras también se han observado contactos intermoleculares del tipo de apilamiento - entre anillos aromáticos, C-H y dímeros no centrosimétricos [57,58].…”

“…La deslocalización electrónica en este fragmento puede ser racionalizada debido a la acción de efectos conjugativos entre el par libre del átomo de nitrógeno con los dobles enlaces C=O y C=S. De acuerdo al análisis tipo NBO realizados por algunos autores al fragmento acil tiourea [56,65], se encontró qué los orbitales de los pares libres (LP) de los átomos de nitrógeno contribuyen fuertemente a las interacciones de resonancia. De este modo, los orbitales LPp(N) actúan como dadores de carga electrónica a los orbitales antienlazantes de baja energía *(C=O) y *(C=S).…”

“…Por otro lado, se notó la ausencia en todas las estructuras cristalinas del contacto C=SH-N, tan solo la tiourea (1) presenta una interacción C=SH-X. Este tipo de interacciones (C=SH-N) contribuyen a la estabilidad de la estructura cristalina, según ha sido publicado por algunos autores[55,56,[66][67][68].…”