Stereochemical Stability of Planar-Chiral Benzazepine Tricyclics: Inversion Energies of P- and S-Alkene Ligands

Inversion barriers ΔG‡ for planar chiral phosphine-alkene and sulfonamide-alkene hybrid ligands based on phenyl-dibenz[b,f]azepine have been determined by density-functional theory calculations. Analysis of the structural and electronic characteristics of the minima and transition states explains the magnitudes of ΔG‡ and the geometrical changes during the inversion process. The steric repulsion caused by bulky substituents attached to the azepine nitrogen atom has a pronounced effect on the ΔG‡ value, explaining, inter alia, the stereochemical stability of the P- and S-alkene ligands when compared to the fluxional parent compound where X = H.

PEG-modified aziridines for stereoselective synthesis of water-soluble fulleropyrrolidines

Diastereoselective synthesis of water-soluble fullerene compounds bearing a pharmacophore pyrrolofullerene-2',5'-dicarboxylate unit is reported. The stereocontrol of the product configuration is achieved through stereospecificity of two consecutive concerted reactions: electrocyclic aziridine ring opening followed by 1,3-dipolar cycloaddition of the resulting azomethyne ylide. The solubility in water (up to 20 μM through direct dissolution) is secured by introducing a polyethylene glycol (PEG) hydrophilic pendant. The structure and molecular-mass distribution of the resulting PEGylated fulleropyrrolidines are exhaustively characterized by 1H, 13C NMR and HRMS. According to absorbance spectroscopy, AFM and DLS studies, the synthesized compound tends to aggregate in aqueous media forming associates of ca. 4-9 nm radius surrounded by a solvation shell resulting in an effective hydrodynamic diameter of ca. 90 nm. In view of notable solubility in water, well-defined chemical structure and resemblance to the compounds with known anti-HIV activity, the synthesized PEGylated diethyl trans-pyrrolofullerene-2',5'-dicarboxylate might be an attractive candidate for biological evaluation.

Molecular iodine-catalysed oxidative CO–C(alkyl) bond cleavage of aryl/heteroaryl alkyl ketones: an efficient strategy to access fused polyheterocycles

An efficient molecular iodine-catalysed one-pot strategy has been accomplished for the construction of various fused heterocycles under metal and oxidant free conditions.

Organocatalytic C(sp3)-H Functionalization via Carbocation-Initiated Cascade [1,5]-Hydride Transfer/Cyclization: Synthesis of Dihydrodibenzo[b,e]azepines

Carbocation-initiated cascade [1,5]-hydride transfer/cyclization and dimerization reactions were developed to synthesize dihydrodibenzo[b,e]azepine and octahydrodipyrroloquinoline derivatives in high yields. These redox-neutral C(sp³)-H functionalization-involving cascade reactions feature transition-metal-free, high atom- and step-economy, and environmental friendliness with water as the sole byproduct.