A rapid and simple diversity-oriented synthesis of novel 3-amino-2′-oxospiro [benzo[c]pyrano[3,2-a]phenazine-1,3′-indoline]-2-carbonitrile/carboxylate derivatives via a one-pot, four-component domino reaction

A review on lawsone-based benzo[a]phenazin-5-ol: synthetic approaches and reactions

Phenazine systems are an important class of aza-polycyclic compounds that are easily found in nature and isolated as secondary metabolites primarily from Pseudomonas, Streptomyces, and a few other genera from soil or marine habitats. Moreover, various synthetic phenazine analogs are known for their pharmaceutical activities. Among various phenazines, benzo[a]phenazines are structural subunits in a variety of important natural products and have been given special attention due to their unique biological properties in various fields. In this review article, we highlight the synthesis of benzo[a]phenazin-5-ol derivatives from lawsone and benzene-1,2-diamines and their applications for the construction of a variety of five and six membered fused heterocycles such as pyranophenazines, spiropyranophenazines, pyridophenazines, furophenazines, benzochromenophenazines and oxazinophenazines during the period of 1995 to 2021.

Photochemical and electrochemical regioselective cross-dehydrogenative C(sp2)–H sulfenylation and selenylation of substituted benzo[a]phenazin-5-ols

The essence of photo- and electrochemistry: sulfenylation and selenylation of substituted benzo[a]phenazin-5-ols through cross-dehydrogenative C(sp2)–H functionalization.

Chitosan-attached nano-Fe3O4 as a superior and retrievable heterogeneous catalyst for the synthesis of benzopyranophenazines using chitosan-attached nano-Fe3O4

A simple and rapid method for the preparation of benzopyranophenazines is presented, involving a one-pot four-component reaction of hydroxynaphthoquinone, o-phenylenediamine, benzaldehydes, and malononitrile with nano-Fe3O4@chitosan as an efficient heterogeneous solid acid catalyst under reflux conditions in ethanol. The catalyst is characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), magnetic susceptibility measurements, energy-dispersive X-ray spectroscopy (EDS), and Fourier transform infrared (FT-IR) spectroscopy. Atom economy, high catalytic activity, a wide range of products, excellent yields in short reaction times, and low catalyst loading are some of the important features of this method.

1,2-Benzoxathiin-4(3H)-one 2,2-dioxide - new enol nucleophile in three-component interaction with benzaldehydes and active methylene nitriles

The reactivity of 1,2-benzoxathiin-4(3H)-one 2,2-dioxide was studied in multicomponent type reactions for the first time, namely, in a three-component interaction with active methylene nitriles and aromatic aldehydes in order to construct condensed 2-amino-4H-pyran derivatives. The reaction outcome strongly depended on the nature of an active methylene nitrile and an arenecarbaldehyde. Application of malononitrile resulted in novel 2-amino-4-aryl-4H-pyrano[3,2-c][1,2]benzoxathiine-3-carbonitrile 5,5-dioxides in most cases, whereas the utilization of ethyl cyanoacetate resulted in a complex mixture of products. In the last case, three different products were isolated depending on the arenecarbaldehyde used, namely ethyl 2-amino-4-aryl-4H-pyrano[3,2-c][1,2]benzoxathiine-3-carboxylate 5,5-dioxides, ethyl 2-cyano-3-arylacrylates, and salts of 3,3′-(arylmethylene)bis(4-hydroxybenzo[e][1,2]oxathiine 2,2-dioxides). Attempts to obtain separately ethyl 2-amino-4-aryl-4H-pyrano[3,2-c][1,2]benzoxathiine-3-carboxylate 5,5-dioxides enabled us to propose reaction pathways leading to these products. The salts were obtained for the first time. The preparative method for the synthesis of triethylammonium salts of 3,3′-(arylmethylene)bis(4-hydroxybenzo[e][1,2]oxathiine 2,2-dioxides) was proposed by the direct interaction of 1,2-benzoxathiin-4(3H)-one 2,2-dioxide with arenecarbaldehydes. The application of ammonium acetate as a catalyst allowed us to synthesize 7-aryl-7,14-dihydrobenzo[5,6][1,2]oxathiino[4,3-b]benzo[5,6][1,2]oxathiino[3,4-e]pyridine 6,6,8,8-tetraoxides containing a novel heterocyclic system. These facts, combined with our past investigations, allowed us to assert that the reactivity of enol nucleophiles that include the COCH₂SO₂X fragment has not been reported previously.

Reactivity of 1,2-benzoxathiin-4(3H)-one 2,2-dioxide was for the first time studied in multicomponent type reactions involving active methylene nitriles and aromatic aldehydes.

An efficient and environmentally sustainable domino protocol for the synthesis of structurally diverse spiroannulated pyrimidophenazines using erbium doped TiO2 nanoparticles as a recyclable and reusable heterogeneous acid catalyst

An efficient and environmentally sustainable domino protocol has been presented for the synthesis of structurally diverse spiroannulated pyrimidophenazines involving a four component reaction of 2-hydroxynaphthalene-1,4-dione, benzene-1,2-diamine, cyclic ketones and amino derivatives in the presence of erbium doped TiO2 nanoparticles as a recyclable and reusable heterogeneous acid catalyst. The present synthetic protocol features mild reaction conditions with operational simplicity, excellent yield with high purity, short reaction time and high atom economy with the use of a recoverable and reusable environmentally sustainable heterogeneous catalyst.

Synthesis, spectral characterization, crystal structure, cytotoxicity and apoptosis-Inducing activity of two derivatives of 2-hydroxy-1,4-naphthaquinone

A phenaxazone compound [5H-Benzo[a]phenoxazin-5-one (BP)] along with an aminoquinone[2-[(o-hydroxyphenyl)amino]-1,4-naphthaquinone (HAN)] derivatives were synthesized from lawsone using ultrasound irradiation technique. The structure of the compounds were characterized by elemental analysis and various spectral studies. Optoelectronic properties were studied using Schrodinger material science suit (2015). The compounds exhibit fluorescence emission in longer wave length it may find applications in photodynamic therapy. Single crystal X-ray diffraction studies reveals that the compound BP crystallizes in monoclinic space group. The antioxidant activity of HAN and BP were determined using DPPH radical scavenging assay and the results indicate that both the compounds have good antioxidant capacity, HAN having more scavenging activity than BP. Lead molecules were identified using in silico molecular docking studies as a green chemistry approach. iGEMDOCK, GOLD and Schrödinger softwares were used for these studies. The docking studies reveal that the structural modification of the parent compound gave more active compounds making them promising lead molecules. The lead molecules were subjected to in vitro studies. The cytotoxicity of BP and HAN was studied using human breast cancer (SKBR3) cell lines. The IC₅₀ value of HAN was found to be 19.8μM while BP was found to have cell viability, less than 10% even at 25μM concentration. The chemotherapeutic agents kill the cancer cells mainly through apoptosis. HAN and BP were subjected to apoptosis studies. BP was found to more active than HAN. Thus it can be suggested that the mechanism of cell death may be through apoptosis.

Recent developments in the isolation, biological function, biosynthesis, and synthesis of phenazine natural products

Phenazines are natural products which are produced by bacteria or by archaeal Methanosarcina species. The tricyclic ring system enables redox processes, which producing organisms use for oxidation of NADH or for the generation of reactive oxygen species (ROS), giving them advantages over other microorganisms. In this review we summarize the progress in the field since 2005 regarding the isolation of new phenazine natural products, new insights in their biological function, and particularly the now almost completely understood biosynthesis. The review is complemented by a description of new synthetic methods and total syntheses of phenazines.

A facile and green approach for the synthesis of spiro[naphthalene-2,5′-pyrimidine]-4-carbonitrile via a one-pot three-component condensation reaction using DBU as a catalyst

A series of novel spiro[naphthalene-2,5′-pyrimidine]-4-carbonitriles were synthesized using 1,3-dimethylbarbituric acid, aldehydes and cyclohexylidene malononitrile in presence of DBU. The structures were confirmed by spectral data and X-Ray crystallography.