Concise Xanthine Synthesis through a Double-Amidination Reaction of a 6-Chlorouracil with Amidines using Base-Metal Catalysis

Synthesis of 5-(trifluoroacetyl)imidazoles from Bromoenones and Benzimidamides via Aza-Michael Initiated Ring Closure Reaction

INTRODUCTION

A simple method for the preparation of 5-(trifluoroacetyl)imidazoles was elaborated.

METHODS

The reaction of trifluoromethyl(α-bromoalkenyl)ketones with benzimidamides was employed to afford the target heterocycles in good yields.

RESULTS

The assembly of imidazole core proceeds via aza-Michael adduct formation followed by intramolecular nucleophilic substitution and spontaneous aromatization as an oxidation sequence.

CONCLUSION

The yields of target imidazoles can be improved by the use of soft oxidizing agents.

Identification of novel 3-aryl-1-aminoisoquinolines-based KRASG12C inhibitors: Rational drug design and expedient construction by CH functionalization/annulation

Developing a synthetic methodology to expediently construct a specific drug scaffold with the desired biological activity remains challenging. Herein, we describe a work on rational application of a synthetic methodology in the synthesis of KRASG12C inhibitors. Novel KRASG12C inhibitors were initially designed with 1-amino-3-aryl isoquinoline scaffold using structure-based drug design strategy. A ruthenium-catalyzed direct monoCH functionalization/annulation cascade reaction of amidines and sulfoxonium ylides was then developed with high versatility of substrates and good tolerance for polar functional groups. By using this reaction, the target compounds 1-amino-3-aryl isoquinolines were facilely prepared. Further in vitro tests led to identification of two novel lead compounds with KRASG12C inhibitory activity.

Synthesis of 4-Aryl Pyrrolo[1,2-α]quinoxalines via Iron-Catalyzed Oxidative Coupling from an Unactivated Methyl Arene

Herein, we describe the direct synthesis of pyrrolo[1,2-α]quinoxaline via oxidative coupling between methyl arene and 1-(2-aminophenyl) pyrroles. Oxidation of the benzylic carbon of the methyl arene was achieved by di-t-butyl peroxide in the presence of an iron catalyst, followed by conversion to an activated aldehyde in situ. Oxygen played a crucial role in the oxidation process to accelerate benzaldehyde formation. Subsequent Pictet-Spengler-type annulation completed the quinoxaline structure. The protocol tolerated various kinds of functional groups and provided 22 4-aryl pyrrolo[1,2-α]quinoxalines when various methyl arene derivatives were used. The developed method proceeded in air, and all catalysts, reagents, and solvents were easily accessible.

Nickel-Catalyzed [4 + 2] Annulation of Nitriles and Benzylamines by C-H/N-H Activation

Nickel-catalyzed [4 + 2] annulation of benzylamines and nitriles via C-H/N-H bond activation, providing straightforward atom-economic access to a wide variety of multisubstituted quinazolines, is reported. Mechanistic investigation revealed that the in situ formed amidines from the coupling of benzylamines and nitriles direct the nickel catalyst to activate the ortho-C-H bond of the phenyl ring of the benzylamine.

One-Pot Synthesis of 4-Quinolone via Iron-Catalyzed Oxidative Coupling of Alcohol and Methyl Arene

Herein, we describe the iron(III)-catalyzed oxidative coupling of alcohol/methyl arene with 2-amino phenyl ketone to synthesize 4-quinolone. Alcohols and methyl arenes are oxidized to the aldehyde in the presence of an iron catalyst and di-tert-butyl peroxide, followed by a tandem process, condensation with amine/Mannich-type cyclization/oxidation, to complete the 4-quinolone ring. This method tolerates various kinds of functional groups and provides a direct approach to the synthesis of 4-quinolones from less functionalized substrates.

Synthesis of Densely Functionalized Pyrimidouracils by Nickel(II)-Catalyzed Isocyanide Insertion

A robust nickel-catalyzed oxidative isocyanide insertion/C–H amination by reaction of readily available N-uracil-amidines with isocyanides affording polysubstituted pyrimidouracils has been reported. The reaction proceeds in moderate to quantitative yield, under mild conditions (i.e., green solvent, air atmosphere, moderate temperature). The broad range of structurally diverse isocyanides and N-uracil-amidines that are tolerated make this method an interesting alternative to the currently available procedures toward pyrimidouracils.

Copper-catalysed C-H functionalisation gives access to 2-aminobenzimidazoles

This paper describes the development, optimisation and exemplification of a copper-catalysed C-H functionalisation to form pharmaceutically relevant 2-aminobenzimidazoles from aryl-guanidines. High throughput screening was used as a tool to identify a catalytically active copper source, DoE was used for reaction optimisation and a range of aryl-guanidines were prepared and exposed to the optimum conditions to afford a range of 2-aminobenzimidazoles in moderate to good yields. The methodology has been applied to the synthesis of Emedastine, a marketed anti-histamine pharmaceutical compound, with the key cyclisation step performed on a gram-scale.

TBHP-mediated oxidative synthesis of substituted pyrimido[4,5-d]pyrimidines fromN-uracil amidines and methylarenes under metal free conditions

An efficient and operationally simple protocol has been demonstrated for the synthesis of 1,3,5,7-tetrasubstituted pyrimido[4,5-d]pyrimidines via TBHP-mediated direct oxidative coupling of N-uracil amidines and methylarenes under metal-free conditions. Due to the inherent stability of methylarenes compared to aldehydes, the presented synthetic protocol is adaptable to a broad substrate scope, is operationally simple, has no need for stringent protection in the whole preparation process, and has the potential to prepare valuable products that are currently inaccessible or challenging to prepare using conventional methods. It is a significantly important complement to the conventional synthetic methods. The reaction possesses an efficient tandem oxidation–imination–cyclization process.

An efficient and operationally simple protocol has been described for the synthesis of 1,3,5,7-tetrasubstituted pyrimido[4,5-d]pyrimidines via TBHP-mediated direct oxidative coupling of N-uracil amidines and methylarenes under metal-free conditions.

Imidazole synthesis by transition metal free, base-mediated deaminative coupling of benzylamines and nitriles

An unprecedented transition metal free, base-mediated deaminative coupling of benzylamines and nitriles is reported. This protocol provides a practical strategy for the synthesis of 2,4,5-tri-substituted imidazoles with liberation of NH₃.