Substituent-controlled regioselective arylation of carbazoles using dual catalysis.

Regioselective arylation of carbazoles is reported using dual palladium-photoredox catalysis. Controlled monoarylation and diarylation of symmetrical and unsymmetrical carbazoles were achieved under mild reaction conditions with a broad substrate scope and functional group tolerance. Steric and electronic control the regioselectivity of the arylation of unsymmetrical carbazoles. Late-stage functionalization of a caprofen drug derivative and large-scale synthesis of mono- and di-arylated carbazoles were demonstrated to showcase the synthetic versatility of the method. Finally, we also showcased the synthesis of hyellazole analogues (a marine alkaloid) in a short route using our strategy.

Rh(III) Catalyzed Redox-Neutral C-H Activation/[5 + 2] Annulation of Aroyl Hydrazides and Sulfoxonium Ylides: Synthesis of Benzodiazepinones.

We herein report the Rh(III) catalyzed redox-neutral C-H activation/[5 + 2] annulation of aroyl hydrazides with sulfoxonium ylides as safe carbene precursors. The reaction shows excellent functional group tolerance, broad substrate scope, and scalability. We demonstrated the synthetic utility of the protocol via the synthesis of various diazepam drug analogues, late-stage functionalization of probenecid drug, and large scale synthesis. Finally, kinetic studies revealed C-H activation as the rate-determining step.

A hydrazine-directed Rh(III) catalyzed (4+2) annulation with sulfoxonium ylides: synthesis and photophysical properties of dihydrocinnolines.

We herein report hydrazine-directed, Rh(III) catalyzed (4+2) annulation of N-alkyl aryl hydrazines with sulfoxonium ylides as a safe carbene precursor. The reaction shows excellent functional group tolerance with broad substrate scope, scalability and site selectivity. Finally, photophysical studies indicated that some of these compounds have interesting fluorescence properties.

Impact of Furan Substitution on the Optoelectronic Properties of Biphenylyl/Thiophene Derivatives for Light-Emitting Transistors.

Biphenylyl/thiophene systems are known for their ambipolar behavior and good optical emissivity. However, often these systems alone are not enough to fabricate the commercial-grade light-emitting devices. In particular, our recent experimental and theoretical analyses on the three-ring-constituting thiophenes end capped with biphenylyl have shown good electrical properties but lack of good optical properties. From a materials science perspective, one way to improve the properties is to modify their structure and integrate it with additional moieties. In recent years, furan moieties have proven to be a potential substitution for thiophene to improve the organic semiconductive materials properties. In the present work, we systematically substituted different proportions of furan rings in the biphenylyl/thiophene core and studied their optoelectronic properties, aiming toward organic light-emitting transistor applications. We have found that the molecular planarity plays a vital role on the optoelectronic properties of the system. The lower electronegativity of the O atom offers better optical properties in the furan-substituted systems. Further, the furan substitution significantly affects the molecular planarity, which in turn affects the system mobility. As a result, we observed drastic changes in the optoelectronic properties of two furan-substituted systems. Interestingly, addition of furan has reduced the electron mobility by one fold compared to the pristine thiophene-based derivative. Such a variation is interpreted to be due to the low average electronic coupling in furan systems. Overall, systems with all furan and one ring of furan in the center end capped with thiophene have shown better optoelectronic properties. This molecular architecture favors more planarity in the system with good electrical properties and transition dipole moments, which would both play a vital role in the construction of an organic light-emitting transistor.

Controlled meta-Selective C-H Mono- and Di-Olefination of Mandelic Acid Derivatives.

Mandelic acids represent a key structural motif present in many drug molecules. Herein, we report the controlled meta-selective mono- and diolefination of mandelic acids by the careful design of the substrate and oxidant. Furthermore, free meta-functionalized mandelic acid was generated by selectively removing the template under mild basic conditions. The synthesis of functionalized homatropine and cyclandelate drug derivatives was demonstrated. Kinetic isotope effects revealed C-H activation as the rate-limiting step.