Versatile and chemoselective transformation of aliphatic and aromatic secondary amides to nitriles

Structural characterization and transformation of nitrogen compounds in waste tire pyrolysis oils

The waste tire pyrolysis oil (WTPO) has been widely concerned because it's a promising recycling method of waste tires. However, the high content of nitrogen in WTPO is unfavorable to its application. In this work, nitrogen compounds in the full distillation range of a waste tire pyrolysis oil were characterized by gas chromatograph-nitrogen chemiluminescence detector (GC-NCD), gas chromatograph-mass spectrometry (GC-MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). In the gasoline fraction of WTPO, the most abundant nitrogen compounds were benzonitrile, aniline and small molecule nitriles. In the diesel fraction of WTPO, the most abundant nitrogen compounds were benzothiazole, quinoline derivatives, p-phthalodinitrile, benzonitrile derivatives, hexadecanenitrile and octadecanenitrile. In the heavy fraction of WTPO, significant amounts of N_xO_y (x = 2-3 and y = 1-2) species were discovered after the separation of solvent dissolution and solid phase extraction. The molecular structures of these N_xO_y species were determined as amide derivatives of diphenylamine by tandem mass spectra of FT-ICR MS. Therefore, the origin of nitriles in the light fractions of WTPO was suspected as the pyrolysis of these amides in the heavy fractions. Finally, the nitrogen transformation during the pyrolysis of waste tires was suggested based on the results of quantum chemistry simulations. These results would be helpful for the treatment and removal of these undesirable nitrogen compounds in WTPO.

Uniting Amide Synthesis and Activation by PIII/PV-Catalyzed Serial Condensation: Three-Component Assembly of 2-Amidopyridines

An organophosphorus (P^III/P^V redox) catalyzed method for the three-component condensation of amines, carboxylic acids, and pyridine N-oxides to generate 2-amidopyridines via serial dehydration is reported. Whereas amide synthesis and functionalization usually occur under divergent reaction conditions, here a phosphetane catalyst (together with a mild bromenium oxidant and terminal hydrosilane reductant) is shown to drive both steps chemoselectively in an auto-tandem catalytic cascade. The ability to both prepare and functionalize amides under the action of a single organocatalytic reactive intermediate enables new possibilities for the efficient and modular preparation of medicinal targets.

Enantioselective assembly of multi-layer 3D chirality

The first enantioselective assembly of sandwich-shaped organo molecules has been achieved by conducting dual asymmetric Suzuki-Miyaura couplings and nine other reactions. This work also presents the first fully C-C anchored multi-layer 3D chirality with optically pure enantiomers. As confirmed by X-ray diffraction analysis that this chiral framework is featured by a unique C2 -symmetry in which a nearly parallel fashion consisting of three layers: top, middle and bottom aromatic rings. Unlike the documented planar or axial chirality, the present chirality shows its top and bottom layers restrict each other from free rotation, i.e., this multi-layer 3D chirality would not exist if either top or bottom layer is removed. Nearly all multi-layered compounds showed strong luminescence of different colors under UV irradiation, and several randomly selected samples displayed aggregation-induced emission (AIE) properties. This work is believed to have broad impacts on chemical, medicinal and material sciences including optoelectronic materials in future.

A redox-neutral synthesis of ketones by coupling of alkenes and amides

The direct synthesis of ketones via carbon-carbon bond formation represents one of the most important challenges in organic synthesis. Hydroacylation of alkenes offers perhaps the most efficient and atom-economical approach for the preparation of ketones employing carbonyl compounds and alkenes as feedstocks. State-of-the-art hydroacylation is typically achieved by a transition metal-catalysed coupling of an aldehyde and an alkene but is plagued by competing decarbonylation, requiring the installation of directing groups in the aldehyde reactant. Herein, we present a method for the hydroacylation of alkenes employing amides in a metal-free regime, proceeding by a new mechanism and offering orthogonal reactivity to the conventional, metal-catalysed alternatives.

Parallel Synthesis of 1H-Pyrazolo[3,4-d]pyrimidines via Condensation of N-Pyrazolylamides and Nitriles

A novel parallel medicinal chemistry (PMC)-enabled synthesis of 1H-pyrazolo[3,4-d]pyrimidines employing condensation of easily accessible N-pyrazolylamides and nitriles has been developed. The presented studies describe singleton and library enablements that allowed rapid generation of molecular diversity to examine C4 and C6 vectors. This chemistry enabled access to challenging alkyl substituents, expanding the overall chemical space beyond that available via typical C(sp²)-C(sp²) coupling and S_NAr transformations. Furthermore, monomer group interconversions allowing the use of larger and more diverse amides and carboxylic acids as precursors to nitriles are discussed.

Direct Regioselective Synthesis of Tetrazolium Salts by Activation of Secondary Amides under Mild Conditions

Tetrazolium salts are biologically active molecules that have found broad applications in biochemical assays. A regioselective synthesis of tetrazolium salts is described through a formal (3 + 2) cycloaddition. The possibility of employing simple amides and azides as starting material and the mild conditions allow a broad functional group tolerance.

Recent advances on the total synthesis of alkaloids in mainland China

Alkaloids are a large family of natural products that mostly contain basic nitrogen atoms. Because of their intriguing structures and important functions, they have long been popular targets for synthetic organic chemists. China's chemists have made significant progress in the area of alkaloid synthesis over past decades. In this article, selected total syntheses of alkaloids from research groups in mainland China during the period 2011–16 are highlighted.