A Highly Efficient Pd(PPh3)4-Catalyzed Suzuki Cross-Coupling Method for the Preparation of 2-Nitrobi­phenyls from 1-Chloro-2-nitrobenz­enes and Phenylboronic Acids

Synthesis of Novel Key Chromophoric Intermediates via C-C Coupling Reactions

The fundamentals of Pd-catalyzed Csp2−Csp2 Miyaura borylation, Suzuki cross-coupling, and Stille cross-coupling reactions for a variety of borylated precursors based on phenothiazine (PTZ), phenoxazine (POZ), carbazole (Cz), and quinoxaline (QX) units have been explored. Three palladium-based catalysts were chosen for this study: Pd(PPh3)4, Pd(PPh3)2Cl2, and Pd(dppf)Cl2, applying different reaction conditions. Around 16 desired chromophores were successfully designed and synthesized using C-C cross-coupling reactions in moderate to excellent yields, including PTZ, POZ, and Cz units coupled with QX, indolinium iodide, thienyl, phenyl, or triphenylamine moieties. Additionally, PTZ, POZ, and Cz have been employed in synthesizing various pinacol boronate ester derivatives in good to moderate yields. Interestingly, Pd(dppf)Cl2 was found to be the best catalyst for borylation, and C-C cross-coupling reactions occurred in as little as 30 min, with an excellent yield exceeding 98%. Pd(PPh3)4 and Pd(PPh3)2Cl2 catalyzed the reaction to obtain the desired products in moderate to good yields after a long time (20–24 h). On the other hand, the Suzuki-Miyaura cross-coupling between N-(2-methyl)hexyl carbazole pinacol boronate ester derivative 10c and three halogenated quinoxaline derivatives—4-(3-(5-bromothiophen-2-yl)quinoxalin-2-yl)benzaldehyde (27), 4-(5-(3-(5-bromothiophen-2-yl)quinoxalin-2-yl)thiophen-2-yl)benzaldehyde (30), and 4-(3-chloroquinoxalin-2-yl)benzaldehyde (25) catalyzed by Pd(PPh3)4—afforded three carbazole-quinoxaline chromophores (28, 30, and 31, respectively) in 2–3 h, with good to excellent yields reaching 86%. The electron-deficient QX couplers proved to be coupled efficiently using the Stille coupling reaction, which involves the coupling between electron-rich orgaostannane and electron-deficient halide. The synthesized precursors and desired chromophores were characterized by FTIR, 1H-NMR, 13C-NMR, and HRMS.

Aqueous Suzuki couplings mediated by a hydrophobic catalyst

The catalytic activity of [(Ph₂P-o-C₆H₄)₂N]PdCl in aerobic aqueous Suzuki couplings is described. Though hydrophobic, this molecular catalyst is competent in cross-coupling reactions of arylboronic acids with a variety of electronically activated, unactivated, and deactivated aryl iodides, bromides, and chlorides upon heating in aqueous solutions under aerobic conditions to give biphenyl derivatives without the necessity of amphiphiles even in the presence of an excess amount of mercury.

Synthesis of 5,7-diarylindoles via Suzuki-Miyaura coupling in water

The synthesis of novel 5,7-diaryl and diheteroaryl indoles has been explored via efficient double Suzuki-Miyaura coupling. The method notably employs a low catalyst loading of Pd(PPh₃)₄ (1.5 mol%/coupling) and water as the reaction solvent to obtain 5,7-diarylated indoles without using N-protecting groups in up to 91% yield. The approach is also suitable for N-protected and 3-substituted indoles and constitutes an important green and convenient arylation strategy for the benzenoid ring of indoles. The synthesized diarylindoles are fluorescent.

Hit to Leads with Cytotoxic Effect in Leukemic Cells: Total Synthesis Intermediates as a Molecule Treasure Chest

A previously designed and developed 12-step total synthesis that includes [1,1'-biphenyl]-2-amine and carbazole intermediates and that ultimately produces the carbazole alkaloid carbazomycin G was exploited as a screening compound library with the goal of identifying potential lead compound(s) with cytotoxic effect. These compounds were investigated by using in-vitro tests involving the two human cell lines HL-60 and MOLM-13, which both model acute myeloid leukaemia (AML). The in-vitro biological test results were used together with the molecular structures of the various intermediates in a concise SAR analysis. Several of the intermediates revealed cytotoxicity (IC₅₀ <10^-4  M), although the final natural product carbazomycin G did not reveal cytotoxicity versus the two said human cell lines.

Ultrasonic accelerated coupling reaction using magnetically recyclable bis (propyl molononitril) Ni complex nanocatalyst: A novel, green and efficient synthesis of biphenyl derivatives

A novel, green and rapid sonochemical research to preparation of the biphenyls was carried out through the coupling reaction between various aryl halides and phenylboronic acid by using bis(propyl malononitrile) Ni (0) complex (NiFe₂O₄@SiO₂-BPMN-Ni) as an efficient nano catalyst. The catalyst can be recycled via an external magnet and reused several times without considerable loss of its catalytic activity. Compare to the previous works, this procedure has advantages such as easy workup, high yields of products, environmentally benign and short reaction times. The novel nickel catalyst prepared and characterized by FT-IR, XRD, SEM, EDX, TGA and VSM techniques.

Synthesis of Boscalidviaa three-step telescoped continuous flow process implemented on a MJOD reactor platform

A three step continuous/semi-flow process leading to the fungicide Boscalid® is disclosed.

An active catalytic system for Suzuki-Miyaura cross-coupling reactions using low levels of palladium loading

An easily available Pd(OAc)₂/(2-(anthracen-9-yl)-1H-inden-3-yl) dicyclohexylphosphine/toluene/ⁱPrOH/water catalytic system was developed, which shows high catalytic activity in the Suzuki-Miyaura cross-coupling reactions of a diverse array of aryl and heteroaryl chlorides with Pd loadings down to 0.01 mol%.