Organotin Compound Derived from 3-Hydroxy-2-formylpyridine Semicarbazone: Synthesis, Crystal Structure, and Antiproliferative Activity

The novel diphenyltin(IV) compound [Ph2(HyFoSc)Sn] (2), where H2HyFoSc (1) is 3-hydroxy-2-formylpyridine semicarbazone, was prepared and characterized by vibrational and NMR (1H, 13C) spectroscopy. The structure of [Ph2(HyFoSc)Sn] was confirmed by single-crystal X-ray crystallography. The doubly deprotonated ligand is coordinated to the tin atom through the enolic-oxygen, the azomethine-nitrogen, and phenolic-oxygen, and so acts as an anionic tridentate ligand with the ONO donors. Two carbon atoms complete the fivefold coordination at the tin(IV) center. Intermolecular hydrogen bonding, C–H → π, and π → π interactions combine to stabilize the crystal structure. Compounds 1 and 2 have been evaluated for antiproliferative activity in vitro against the cells of three human tumor cell lines: MCF-7 (human breast cancer cell line), T24 (bladder cancer cell line), A549 (nonsmall cell lung carcinoma), and a mouse fibroblast L-929 cancer cell line

(±)-Cyclo­hexane-1,2-diyl bis­(4-nitro­benzoate)

The crystal structure of the title compound, C20H18N2O8, has been investigated to establish the relative stereochemistry between the ester groups. The cyclo­hexane ring adopts a chair conformation, in which the two ester groups occupy the adjacent equatorial positions in a trans relationship with each other. The mol­ecules assemble in the crystal as chains along the c axis via C—H⋯π inter­actions between the cyclo­hexane ring and a pair of nitro­phenyl rings of the neighbouring mol­ecule. Also observed are π–π stacking inter­actions between the nitro­phenyl rings of neighbouring chains, with a perpendicular distance between these rings of 3.409 Å and a slippage of 0.969 Å

Stable Hemiaminals: 2-Aminopyrimidine Derivatives

Stable hemiaminals can be obtained in the one-pot reaction between 2-aminopyrimidine and nitrobenzaldehyde derivatives. Ten new hemiaminals have been obtained, six of them in crystal state. The molecular stability of these intermediates results from the presence of both electron-withdrawing nitro groups as substituents on the phenyl ring and pyrimidine ring, so no further stabilisation by intramolecular interaction is required. Hemiaminal molecules possess a tetrahedral carbon atom constituting a stereogenic centre. As the result of crystallisation in centrosymmetric space groups both enantiomers are present in the crystal structure

The DFT study on the reaction between benzaldehyde and 4-amine-4H-1,2,4-triazole and their derivatives as a source of stable hemiaminals and schiff bases. Effect of substitution and solvation on the reaction mechanism

Reaction mechanism for the benzaldehyde (ald) and 4-amine-4H-1,2,4-triazole (4at) has been investigated at the DFT (B3LYP)/6–31+G(d) computational level. Three transition states (TS) have been identified. The TS1 corresponds to hydrogen transfer from the NH2 group to the C = O bond and nucleophillic attack of the carbon atom from the aldehyde group on the nitrogen atom from the NH2 group in 4at. The result of this reaction is the hemiaminal molecule. The TS2 characterises an internal rearrangement of the benzene and triazole rings in the hemiaminal molecule. The TS3 leads to breaking of the O-H bond, the elimination reaction of the H2O molecule, and formation of the C=N bond. The final product of this reaction is a Schiff base. In order to determine the most favorable conditions for hemiaminal formation, the influence of electronic structure modification on the energetic properties during the reaction of benzaldehyde and 4-amine-4H-1,2,4-triazole has been studied. Thirteen substituents: NH2, OH, OCH3, CH3, F, I, Cl, Br, COH, COOH, CF3, CN, NO2, with different Hammett’s constant values (σ = −0.66–+0.78) have been considered. Finally, the reaction mechanism has been investigated in the presence of 1 to 5 water molecules

Why Is the Resolution of Certain Racemic Modifications Inefficient? Formation of Diastereomeric Double Salts of Brucinium

Fractional crystallization of diastereomeric salts remains the most frequently used method for a separation of racemic compounds, and yet it has been performed by trial and error. For a better understanding of the chiral discrimination mechanism that is useful for the rationalization of optical resolution and help in choosing the crucial experimental parameters, structural investigations of products of both successful and unsuccessful racemic resolution are important. The former and the latter typically involve diastereomeric salts precipitating fractionally and the formation of solid solutions of diastereomeric salts or diastereomeric double salts, respectively. In this contribution, a mechanism of recognition leading to formation of the diastereomeric double salts is proposed based on crystal structures of three brucinium double salts (bis­(brucinium) <i>N</i>-(3,5-dinitrobenzoyl)-dl-alaninate methanol 3-solvate, bis­(brucinium) <i>N</i>-(3,5-dinitrobenzoyl)-dl-alaninate 5.75-hydrate, and bis­(brucinium) <i>N</i>-(3,5-dinitrobenzoyl)-dl-serinate 0.10-hydrate) as well as of some relevant diastereomeric salts (containing the d- or l-enantiomer of the alanine or the serine derivative)