Polythiourethane Covalent Adaptable Networks for Strong and Reworkable Adhesives and Fully Recyclable Carbon Fiber-Reinforced Composites.

The development of adhesives with superior optical and mechanical performance, solvent resistance, and reworkability is gaining increasing attention in recent years. However, traditional materials do not possess reprocessability and healing characteristics for sustainable development. Here, a superior dynamic polythiourethane (PTU) adhesive with high reprocessability was developed by introducing covalent adaptable networks (CANs). Specifically, dynamic thiocarbamate bonds (TCB) were used to prepare PTU CANs, which showed dramatically enhanced malleability and recyclability. The Young's modulus of the material was 2.0 GPa and the tensile strength was 62.7 MPa. The reprocessing temperature of CANs was reduced to 80 °C while more than 90% of their mechanical properties were retained, even after being reprocessed several times. Moreover, the highly transparent and water-resistant PTU CANs featured an excellent bonding property and reworkability for various materials including glass, with a lap shear strength of 2.9 MPa, metal (5.1 MPa), and wood (6.3 MPa), compared with commercially available adhesives. Additionally, carbon fiber-reinforced composites constructed with PTU CANs were capable of being fully recycled and reused. Importantly, laminated glass with a toughened PTU-PU elastomer interface exhibited an outstanding impact fatigue-resistance behavior, sustaining thousands of impacts. These features demonstrate that PTU CANs show great potential as sustainable materials.

Rhodium(III)-Catalyzed Diastereoselective Ring-Opening of 7-Azabenzonorbornadienes with Aromatic Ketoximes: Synthesis of Benzophenanthridine Derivatives.

A rhodium(III)-catalyzed redox-neutral ring-opening of 7-azabenzonorbornadienes with aromatic ketoximes giving 2-arylated hydronaphthylamines in a highly diastereoselective manner is described. Later, the 2-arylated hydronaphthylamines were converted into highly sensitive 13,14-dehydro benzophenanthridine derivatives by HCl hydrolysis. Further, 13,14-dehydro benzophenanthridines were aromatized into biologically important benzophenanthridine derivatives in the presence of DDQ. A possible reaction mechanism was proposed and supported by deuterium labeling studies and isolation of a rhodacycle intermediate.

A facile one pot synthesis of thiazolo[3,2-a]benzimidazole and pyran fused polyheterocyclic scaffolds.

An efficient synthesis of dihydro-4H-benzo[4,5]imidazo[2,1-b]pyrano[2,3-d]thiazole by a multicomponent route starting from 2-((1H-benzo[d]imidazol-2-yl)thio)-1-phenylethan-1-one, an aromatic aldehyde and malononitrile is described. This protocol features a metal free approach with good substrate scope and decent yield. The heterocyclic skeleton obtained in this study may have interesting biological properties.

Remote alkylation of N-(quinolin-8-yl)benzamides with alkyl bromides via ruthenium(ii)-catalyzed C-H bond activation.

A ruthenium(ii) catalyzed remote C-5 alkylation of the quinoline ring of N-(quinolin-8-yl)benzamides with alkyl bromides via C-H bond activation is described. Various substituted N-(quinolin-8-yl)benzamides reacted with tertiary or secondary or primary alkyl bromides giving the alkylated products in good to moderate yields. Herein, the ruthenium catalyzed remote C-5 alkylation is effected via aromatic C-H bond activation as a key step. It has been proved by the deuterium labelling studies and mechanistic investigations.

Hypervalent Iodine(III) Mediated Synthesis of 3-Substituted 5-Amino-1,2,4-thiadiazoles through Intramolecular Oxidative S-N Bond Formation.

An efficient synthesis of 3-substituted-5-arylamino-1,2,4-thiadiazoles through intramolecular oxidative S-N bond formation of imidoyl thioureas by phenyliodine(III) bis(trifluoroacetate) is reported. The protocol features a metal-free approach, broad substrate scope, very short reaction times, good to excellent yields, and simple starting materials.

Investigation on the reactivity of α-azidochalcones with carboxylic acids: Formation of α-amido-1,3-diketones and highly substituted 2-(trifluoromethyl)oxazoles.

The reaction of α-azidochalcones with carboxylic acids has been investigated resulting in the formation of α-amido-1,3-diketones under microwave irradiation via in situ formation of 2H-azirine intermediates. An interesting reaction is described wherein, with trifluoroacetic acid at lower temperature, it affords highly substituted 2-(trifluoromethyl)oxazoles. These flexible transformations proceed under solvent free conditions in good to excellent yields without any catalyst.

Erbium triflate promoted multicomponent synthesis of highly substituted imidazoles.

The synthesis of highly substituted imidazole derivatives has been achieved from various α-azido chalcones, aryl aldehydes, and anilines. This multicomponent protocol employs erbium triflate as a catalyst resulting in excellent yield of the imidazoles.