Convenient Synthesis of 11-Substituted 11H -Indolo[3,2-c ]quinolines by Sequential Chemoselective Suzuki Reaction/Double C-N Coupling

Preparation of 3,5-Methanobenzo[b]azepines: An sp3-Rich Quinolone Isostere

The replacement of the aromatic ring in bioactive compounds with saturated bioisosteres has become a popular tactic to obtain novel structures with improved physicochemical profiles. In this paper, we describe an efficient synthesis of 3,5-methanobenzo[b]azepine analogues and suggest them as isosteres of quinolones. Quinolones are heteroaromatic, flat rings and considered as privileged scaffolds. An isosteric version of this scaffold with more 3D character would offer new options to expand their use.

Condition-Dependent Selective Synthesis of Indolo[1,2-c]quinazolines and Indolo[3,2-c]quinolines from 2-(1H-Indol-2-yl)anilines and Sulfoxonium Ylides

In this paper, a selective synthesis of indolo[1,2-c]quinazolines and indolo[3,2-c]quinolines through the cascade reactions of 2-(1H-indol-2-yl)anilines with sulfoxonium ylides is presented. The formation of products involves the generation of a carbene species from sulfoxonium ylide and its N-H bond insertion reaction with 2-(1H-indol-2-yl)aniline followed by deoxygenative imine formation, intramolecular N- or C- nucleophilic addition and deoxygenative aromatization. This switchable synthesis was condition-dependent. In the presence of K₂CO₃ in CH₃CN, the reaction mainly furnished indolo[1,2-c]quinazolines. In the presence of HOAc in dioxane, it selectively afforded indolo[3,2-c]quinolines. In addition, direct C-H/N-H functionalization of the products obtained provides a convenient and direct access to polycyclic heteroaromatic compounds. These novel protocols have advantages such as readily accessible substrates, easily tunable selectivity, good compatibility with diverse functional groups, and the use of air as a cost-free and sustainable oxidant.

Palladium-Catalyzed Synthesis of Heterocyclic Ring Systems by Combination of Regioselective C–C with Twofold C–N Couplings

The combination of regioselective palladium-catalyzed C–C with twofold C–N couplings allows for the synthesis of a variety of heterocyclic ring systems. Starting materials include thiophenes and benzothiophenes, pyrroles and indoles, furans and benzofurans, pyridines, quinolines and quinoxalines, complex heterocyclic systems and benzophenone derivatives. The products are in many cases complex polyheterocyclic systems, which are not readily available by other methods or, in a number of cases, were not described in the literature before. They are of pharmacological relevance or interesting in the field of material science. Products include thieno[3,2-b:4,5-b′]diindoles, thieno[3,2-b]indoles, thieno[3,4-b]indoles, 5,10-dihydroindolo[3,2-b]indoles, furo[3,2-b:4,5-b′]diindoles, benzo[4,5]furo[3,2-b]indoles, 5,7-dihydropyrido[3,2-b:5,6-b′]diindoles, 5,7-dihydropyrido[2,3-b:6,5-b´]diindoles, α-, β-, γ- and δ-carbolines, indolo[3,2-b]quinolines, indolo[2,3-b]quinolines, indolo[3,2-c]quinolines, indoloquinoxalines, pyrido[2′,1′:2,3]imidazo[4,5-b]indoles, thiadiazolo[2′,3′:2,3]imidazo[4,5-b]indoles, benzo[b]carbazolediones, acridones and thieno[3,2-b]quinolones.

Contents

1 Introduction

2 Thiophenes and Benzothiophenes

3 Pyrroles and Indoles

4 Furans and Benzofurans

5 Pyridines

6 Quinolines and Quinoxalines

7 Complex Heterocyclic Systems

8 2,3-Dibromonaphthoquinone

9 Benzophenone Derivatives

10 Conclusions

Synthesis of indolo- and benzothieno[3,2-c]quinolines via POCl3 mediated tandem cyclization of o-alkynylisocyanobenzenes derived from o-alkynyl-N-phenylformamides

A synthesis of indolo[3,2-c]quinolines and benzothieno[3,2-c]quinolines has been developed employing o-alkynyl-N-phenylformamide derivatives as the substrates. The reaction proceeded via a tandem process involving POCl3‒assisted intramolecular cyclization of the firstly formed...

Advancements in the synthesis of fused tetracyclic quinoline derivatives

Fused tetracyclic systems containing a quinoline nucleus represent an important class of heterocyclic bioactive natural products and pharmaceuticals because of their significant and wide-spectrum biological properties. Several of these compounds have been obtained with diverse pharmacological and biological activities, such as antiplasmodial, antifungal, antibacterial, potent antiparasitic, antiproliferative, anti-tumor and anti-inflammatory activities. This information will be beneficial for medicinal chemists in the field of drug discovery to design and synthesize new fused tetracyclic quinolines as potent therapeutical agents. This review article provides a comprehensive report regarding the methods developed for the synthesis of fused tetracyclic quinolines reported so far (till October 2019). The article includes synthesis by one-pot domino reaction, microwave synthesis using a catalyst, using ionic liquids, photocatalytic synthesis (UV radiation), Pfitzinger reaction, I2-catalyzed cyclization reaction, Wittig reaction, cascade reaction, imino Diels-Alder reaction, Friedel-Crafts reaction, CDC reaction, solvent-free reactions and using small chiral organic molecules as catalysts. To the best of our knowledge, this is the first review focused on the synthesis of fused tetracyclic quinolines along with mechanistic aspects.

Recent Advances in the Hofmann Rearrangement and Its Application to Natural Product Synthesis

:

C-N bond formation reactions are the most important transformations in (bio)organic chemistry because of the widespread occurrence of amines in pharmaceuticals, natural products, and biologically active compounds. The Hofmann rearrangement is a well-known method used for the preparation of primary amines from amides. But, the traditional version of the Hofmann rearrangement often gave relatively poor yields due to over-oxidation or due to the poor solubility of some amides in aqueous base, and created an enormous amount of waste products. Developments over the last two decades, in particular, have focused on refining both of these factors affecting the reaction. This review covers both the description of recent advances (2000-2019) in the Hofmann rearrangements and its applications in the synthesis of heterocycles, natural products and complex molecules of biological interest. It is revealed that organo-catalytic systems especially hypervalent iodine-based catalysts have been developed for the green and environmentally friendly conversion of carboxamides to primary amines and carbamates.