Molecular self-assembly and optical activity of chiral thionooxalamic acid esters
摘要:
Three chiral bisthionooxalamides were synthesized by acylation with ethyl or (1R)-menthyl chloroxoacetate of the corresponding diamines and subsequent thionation with Lawesson's reagent. Single crystal X-ray diffraction analysis revealed that products 4b-7b self-assemble in the solid state by the ring [N-H center dot center dot center dot O=C, R-2(2) (10)] or chain [N-H center dot center dot center dot S=C, C(4)] hydrogen-bond motifs. Only in the 2 case of 4b was a helical superstructure formed. In racemic compound 6b, the molecules are connected via N-H center dot center dot center dot S=C hydrogen bonds into homochiral chains, similar to those formed in 7b. The solid state CD spectra of chiral bisthionooxalamides are characterized by strong Cotton effects in the region of the thioamide n-pi* transition. Their sign is determined by the helicity of the S=C-C=O unit. (c) 2007 Elsevier Ltd. All rights reserved.
Supramolecular structures of bis-thionooxalamic acid esters derived from (±)-cyclohexane-1,2-diamine and (±)-1,2-diphenylethylenediamine
摘要:
The bis-thionooxalamic acid esters trans-(+/not superset of)-diethyl N, N'-(cyclohexane-1,2-diyl)bis(2-thiooxamate), C14H22N2O4S2, and (+/not superset of)-N,N'-diethyl (1,2-diphenylethane-1,2-diyl)bis(2-thiooxamate), C22H24N2O4S2, both consist of conformationally flexible molecules which adopt similar conformations with approximate C-2 rotational symmetry. The thioamide and ester parts of the thiooxamate group are significantly twisted along the central C-C bond, with the S = C-C = O torsion angles in the range 30.94 (19) - 44.77 (19)degrees. The twisted s-cis conformation of the thionooxamide groups facilitates assembly of molecules into a one-dimensional polymeric structure via intermolecular three-center C = S center dot center dot center dot NH center dot center dot center dot O = C hydrogen bonds and C-H center dot center dot center dot O interactions formed between molecules of the opposite chirality.
New chiral chelating C-2 bis-oxazoline-amide ligands (1) exhibiting a highly flexible molecular structure have been prepared in high yield through a versatile synthetic pathway. Combined crystallographic, variable temperature (VT)-NMR, IR, and ESI-MS studies have been carried out to investigate the nature of the 1-Pd complexes that are effective tools in controlling the stereochemical outcome of Pd-catalyzed allylic alkylations (ee up to 98%).