Comparison of racemization processes in 1-arylpyrimidine-2-thione and 3-arylthiazoline-2-thione atropisomers and their oxygen analogs

An approach to discriminating 25 commercial chiral stationary phases from structural data sets extracted from a molecular database

“…As steric effects often play a major role in the molecular environment of axial or planar dissymmetrical compounds its not surprising to find on the same side the descriptor CHI. As could be expected from literature trends, the CSPs CTA and OT show a good success for such chiral compounds (Roussel et al, 1988;Mannschreck et al, 1987;Meurer et al, 1985). In the same way, the behaviour of the other CSPs may be summarized as following: -OK and OB located at the neighbourhood of ROR and EST (ether and ester) appear to be CSPs of choice for oxygenated solutes -OA, SPH, OJ have a good affinity for solutes containing an asymmetric centre on a cycle -Derivatization of carboxylic acids in ester is recommended for OA, OB, OK, OJ, SPH, OT, CTA -OA, OB, OK have a very low affinity for basic solutes -OF and OJ show good results in the resolution of basic compounds -PCO and PIO (Pirkle ionic) exhibit good results when carboxylic acids are derived in amides or esters respectively.…”

Synthesis, characterization and density functional theory investigations of monoacyl aniline derivatives

“…After work-up, N-(2-methoxy-phenyl)-4-nitro-benzamide was obtained as a yellow crystals shiny, yield 4 …”

“…Electronaccepting groups are supposed to increase the rotation energy barrier in contrast to electrondonating groups. The influence of the resonance and the field effect of amino and nitro groups on the electron density in the phenyl ring and the respective accelerating and decelerating effects on the rate of enantiomeriazation of atropisomerc biphenyls has been investigated [4]. Amide barriers to rotation have been studied extensively [5].…”

Breaking the Symmetry of Axially Chiral N‐Aryl‐2(1H)‐pyrimidinones by Spontaneous Crystallization

“…[9] Four pyrimidin-2(1H)-ones (1 a-d, Figure 1) were synthesized which have a variety of aryl groups with substituents at the ortho and/or other positions. [10,11] To determine whether each pyrimidinone affords conglomerate or racemic crystals, each single crystal was analyzed by HPLC employing Chiral Cell OJ and OD columns (Daicel Chemical Industry). In the HPLC analysis of single crystals of pyrimidinone 1 b two peaks arise from the two enantiomers in the ratio of 1:1.…”

“…Roussel et al also studied similar pyrimidinone derivatives independently and proposed a different mechanism for racemization via an open form. [11] The rate of enantiomerization of the chiral pyrimidinones 1 a, 1 c, and 1 d was studied in three kinds of solvents: xylene (nonpolar and aprotic), dimethylformamide (DMF; polar and aprotic), and 1-propanol (polar and protic). Each enantiomorphic crystal obtained from usual crystallization was dissolved in the solvent, and the rate of enantiomerization at three temperatures (70, 80, and 90 8C) was followed by HPLC with the Chiral Cell OD columun.…”