A Preliminary Study of Thermosets from Epoxy Resins Made Using Low-Toxicity Furan-Based Diols.

Glycidyl ethers are prepared from a series of furan-based diols and cured with a diamine to form thermosets. The furan diols demonstrate lower toxicity than bisphenol-A in a prior study. The diglycidyl ethers show improved thermal stability compared to the parent diols. Cured thermosets are prepared at elevated temperature using isophorone diamine (IPDA). Glass transition temperatures are in the range of 30-54 °C and depend on the structure of the furan diol. Coatings are prepared on steel substrates and show very high hardness, good adhesion, and a range of flexibility. Properties compare favorably with a control based on a bisphenol-A epoxy resin. The study demonstrates that epoxy resins based on furan diols, which have been shown to have lower toxicity than bisphenol-A, can form thermosets having properties comparable to a standard epoxy resin system; and thus, are viable as replacements for bisphenol-A epoxy resins.

Lead-oriented synthesis of epigenetic relevant scaffolds.

A simple and rational method to rank lead-likeness of molecules using continuous evaluation functions was hereby developed. This strategy proved to be competitive against known methods and finally helped in driving synthetic efforts towards candidates of interest for epigenetic applications against HDAC6, BRD4 and EZH2.

Recent advances in the global ring functionalization of 7-azaindoles.

The 7-azaindole building block has attracted considerable interest in the field of drug discovery in the current portfolio. Because of their powerful medicinal properties, the development of synthetic, elegant techniques for the functionalization of 7-azaindoles continues to be an active area of research. Advances in metal-catalyzed chemistry have recently supported the successful development of a number of novel and effective methods for functionalization of the 7-azaindole template. This review reports state-of-the-art functionalization chemistry of 7-azaindoles with an aspiration to highlight the global ring functionalization of 7-azaindoles that are potential as pharmacophores for various therapeutic targets. Other relevant reviews focused on 7-azaindole synthesis, properties and applications have also been reported. However, none of these reviews have been dedicated to the results achieved in the field of metal-catalyzed cross-coupling/C-H bond functionalized reactions. So we wish to discuss and summarize the advances made since 2011 in this field toward 7-azaindole functionalization.

Programmed synthesis of triarylnitroimidazoles via sequential cross-coupling reactions.

Transition-metal-catalyzed programmed sequential arylation reactions of 2-chloro-4-nitro-1H-imidazoles were achieved. The methods are general and were applied in a chemoselective manner for the synthesis of different multiarylated 4-nitroimidazoles bearing three different aryl groups. A salient feature is Pd-catalyzed hetero-hetero coupling at the C5 position through a NO2 directed cross-dehydrogenative coupling (CDC) approach.

Palladium-catalyzed aminocarbonylation of halo-substituted 7-azaindoles and other heteroarenes using chloroform as a carbon monoxide source.

A palladium-catalyzed aminocarbonylation of halo-substituted 7-azaindoles utilizing CHCl3 as the carbonyl source has been developed for the straightforward incorporation of an amide functional group. The protocol was extended to other heteroarenes such as pyrazolopyridines and indazoles. The substrate scope of the reaction with respect to heteroarenes and the amine component is reported. This method offers an alternative avenue for aminocarbonylation of pharmaceutically important heterocycles.

Ruthenium-catalyzed site-selective C-H arylation of 2-pyridones and 1-isoquinolinones.

An efficient Ru(ii)-catalyzed site-selective C-H arylation of 2-pyridones and 1-isoquinolinones was achieved with boronic acids by using pyridine as a directing group. The developed protocol is general and provides rapid access to an array of C6-arylated 2-pyridones and C3-arylated 1-isoquinolinones in excellent yields. These designed arylated 2-pyridones and 1-isoquinolinones can serve as key structural motifs for accessing functionalized pyridines and isoquinolines.

Nickel-catalyzed Chan-Lam cross-coupling: chemoselective N-arylation of 2-aminobenzimidazoles.

A complementary set of Ni- and Cu-based catalyst systems for the selective N-arylation of 2-aminobenzimidazoles have been developed. Selective N-arylation of the primary amine (C-NH2) group was achieved by Ni-catalyzed, boronic acid promoted cross-coupling reactions in air, whereas, selective N-arylation of the azole nitrogen was achieved with Cu-catalysis and aryl halides. These protocols are general and give rapid access to an array of both the N-arylated isomers of 2-aminobenzimidazoles.

Site-Selective Intermolecular Oxidative C-3 Alkenylation of 7-Azaindoles at Room Temperature.

A previously unexplored palladium-catalyzed C-3 selective alkenylation of 7-azaindoles, performed in the presence of Pd(OAc)2 as the catalyst, PPh3 as the ligand, Cu(OTf)2 as an oxidative cocatalyst, and molecular oxygen (O2) as the terminal oxidant at room temperature, has been reported. This direct alkenylation strategy offers a new approach in functionalizing pharmaceutically important 7-azaindoles.

Divergent synthesis of 4,6-diarylated pyridin-2(1H)-ones from chalcones: novel access to 2,4,6-triaryl pyridines.

A wide range of 4,6-diarylated/heterylated pyridin-2(1H)-one derivatives were synthesized in good to excellent yields from 1,3-diarylated/heterylated-2-propen-1-ones (chalcones) in one pot under metal and base-free conditions. This domino reaction suggests a novel mechanism comprising of Michael addition followed by amination, subsequent intramolecular amidation and finally dehydronitrosation. The usefulness of the designed 4,6-diarylated/heterylated pyridin-2(1H)-one derivatives has further been demonstrated by synthesizing medicinally important 2,4,6-triaryl/heteryl pyridines via Pd-catalyzed cross-coupling reaction.

Cu-catalyzed arylation of the amino group in the indazole ring: regioselective synthesis of pyrazolo-carbazoles.

Cu(II)-catalyzed cross-coupling of various aryl boronic acids with 5 and 6-amino indazoles has resulted in (arylamino)-indazoles. These (arylamino)-indazoles have been utilized in synthesizing medicinally important pyrazole-fused carbazoles via Pd(II)-catalyzed cross-dehydrogenative coupling (CDC). This combined N-arylation/C-H arylation strategy has been successfully applied to the regioselective synthesis of polyheterocycles 3,6-dihydropyrazolo[3,4-c]carbazoles and 1,6-dihydro pyrazolo[4,3-c]carbazoles. Quantum chemical analysis has been carried out to understand the regioselectivity and to trace the potential energy surface of the entire reaction upon 5-N-aryl-indazole conversion to the corresponding carbazole.

Direct C-2 arylation of 7-azaindoles: chemoselective access to multiarylated derivatives.

Pd-catalyzed direct C-H arylation of N-methyl-7-azaindole at the C-2 position by diverse arylboronic acids was achieved at room temperature. The method is general and was applied in chemoselective synthesis of multiarylated 7-azaindole derivatives bearing three different aryl groups at the 2, 3, and 5 positions.