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Hit, Lead & Candidate Discovery In recent studies, we have shown that pyrrolo[3,4-f]indole-5,7-dione and indole-5,6-dicarbonitrile derivatives act as good potency in vitro inhibitors of the monoamine oxidase (MAO) enzymes. To expand on these series and to further derive structure-activity relationships (SARs) for MAO inhibition, in the present study we synthesized additional homologs and related analogs of these chemical classes. Analyzes of the MAO inhibition properties of the synthesized compounds show that among the pyrrolo[3,4-f]indole-5,7-dione derivatives good potency MAO inhibitors exist as exemplified by 10, which possesses IC50 values for the inhibition of MAO-A and MAO-B of 0.023 and 0.178 µM, respectively. Among thirteen pyrrolo[3,4-f]indole-5,7-diones, nine compounds exhibit IC50 values for the inhibition of an MAO isoform in the submicromolar range. It may be concluded that active MAO inhibitors, such as 10 represent suitable leads for the development of drugs for neurodegenerative and neuropsychiatric disorders such as Parkinson's disease and depression. MAO inhibitors are also of interest for the treatment of prostate cancer, certain types of cardiomyopathies and Alzheimer's disease.

Series of structurally diverse 2-imidazoline derivatives have been synthesized by condensation of substituted aldehydes with ethylenediamine, Pd-catalyzed N-arylation of 2-imidazolines and by the formation of 1,2,4-oxadiazoles and benzoxazepines from 2-imidazoline-containing precursors. The 2-imidazoline derivatives were evaluated as potential inhibitors of human monoamine oxidase (MAO) A and B. Among the 2-imidazolines, good potency inhibitors were discovered with compound 9p (IC50 = 0.012 µM) being the most potent MAO-B inhibitor, while compound 9d (IC50 = 0.751 µM) was the most potent MAO-A inhibitor of the series. These potencies are in the same range as those of reference MAO inhibitors used in the clinic. Among 33 compounds evaluated, 13 exhibited IC50 values in the submicromolar range for the inhibition of an MAO isoform. It is postulated that the imidazoline moieties of some of these inhibitors may be recognized by the imidazoline I2-binding site of MAO. Good potency MAO inhibitors may be useful for the treatment of neuropsychiatric and neurodegenerative disorders such as depression and Parkinson’s disease, and future application for the treatment of prostate cancer, congestive heart failure and Alzheimer’s disease. In addition, high potency 2-imidazoline-derived MAO inhibitors may be used as potential probes for the imidazoline binding sites of the MAOs, as well as to determine alternative binding regions of imidazoline within the MAO active site.

In recent studies, we have investigated the monoamine oxidase (MAO) inhibition properties of pyrrolo[3,4-f]indole-5,7-dione and indole-5,6-dicarbonitrile derivatives. Since numerous high potency MAO inhibitors are present among these chemical classes, the present study synthesizes 44 additional derivatives in an attempt to further derive structure-activity relationships (SARs) and to establish optimal substitution patterns for MAO inhibition. The results show that, with the exception of one compound, all indole-5,6-dicarbonitrile derivatives (10) exhibit submicromolar IC50 values for the inhibition of MAO, with the most potent MAO-A inhibitor exhibiting an IC50 value of 0.006 μM while the most potent MAO-B inhibitor exhibits an IC50 value of 0.058 μM. Interestingly, an N-oxide derivative (4c) also proved to be a potent and nonspecific MAO inhibitor. With the exception of one compound, all of the pyrrolo[3,4-f]indole-5,7-diones (28) also exhibit submicromolar IC50 values for the inhibition of an MAO isoform. The most potent inhibitor exhibit an IC50 value of 0.011 μM for MAO-A. This study proposes that high potency MAO inhibitors such as those investigated here, may act as lead compounds for the development of treatments for neurodegenerative and neuropsychiatric disorders such as Parkinson's disease and depression.

The monoamine oxidase (MAO) enzymes are key metabolic enzymes of neurotransmitter and other bioactive amines, and represent important drug targets for the treatment of neuropsychiatric and neurodegenerative disorders. Inhibitors of MAO are established medications for the treatment of depression and Parkinson’s disease, and may have future roles in other disease states such as the therapy of prostate cancer, cardiovascular disease and inflammatory diseases. Based on these considerations, the present study synthesizes a series of 22 pyrazolo[1,5-a]quinoxalin-4-one derivatives and evaluated them as potential inhibitors of human MAO-A and MAO-B. The results show that 8 derivatives inhibit MAO-A, and 3 derivatives inhibit MAO-B with IC50 values in the submicromolar range (

The C-3 acylation of 1-hydroxyindole derivatives with aliphatic acid anhydrides was accomplished in high yields using BF3·Et2O as a promoter, affording the corresponding 3-acyl-1-acyloxyindoles which in turn were readily hydrolyzed to the corresponding 3-acyl-1-hydroxyindole derivatives.

Recent studies have found that phthalonitrile derivatives are remarkably potent inhibitors of human monoamine oxidase (MAO) A and B. In an attempt to further determine the structure-activity relationships (SARs) for MAO inhibition by this class of compounds and to discover novel potent MAO inhibitors, the present study investigated the MAO inhibition properties of a series consisting of indole‐5,6‐dicarbonitrile derivatives. The results document that 3‐chloro‐1H‐indole‐5,6‐dicarbonitrile derivatives exhibited potent inhibition of the MAOs. For example, 3‐chloro‐2‐(4‐methylphenyl)‐1H‐indole‐5,6‐dicarbonitrile inhibited MAO-A and MAO-B with IC50 values of 0.014 μM and 0.017 μM, respectively. It was further shown that this compound acts as a reversible and competitive inhibitor of both MAO isoforms. An analysis of the SARs for MAO inhibition by 3‐chloro‐1H‐indole‐5,6‐dicarbonitriles showed that methylation of the indole nitrogen eliminates MAO-B inhibition activity, and replacement of the 2-phenyl ring with the thienyl results in a 9-fold reduction of MAO-B inhibition activity. A series of 3‐bromo‐1-hydroxy‐1H‐indole‐5,6‐dicarbonitriles are, in turn, comparatively weaker MAO inhibitors. It may be concluded that indole-5,6-dicarbonitrile derivatives are suitable leads for the design MAO inhibitors for the treatment of disorders such as Parkinson’s disease and depression Medical Research Council and National Research Foundation of South Africa (Grant specific unique reference numbers (UID) 85642 and 80647)

10-Aryl-2-oxo-2,3-dihydro-1H-[1,2,4]oxadiazino[2,3-a]indole-7,8-dicarbonitriles were obtained in two steps from the corresponding 2-amino-1-hydroxyindoles and methyl bromoacetate.

The Vilsmeier–Haack formylation of 4-(2-aryl-2-oxoethyl)-5-nitrophthalonitriles followed by reduction affords 3-acyl-1-hydroxy- 1H-indole-5,6-dicarbonitriles.

The Vilsmeier–Haack formylation of 4-(2-aryl-2-oxoethyl)-5-nitrophthalonitriles followed by reduction affords 3-acyl-1-hydroxy- 1H-indole-5,6-dicarbonitriles.

Reactions of 4-bromo-5-nitrophthalonitrile (BNPN) with enolates of alkyl 4-R-2,4-dioxobutanoates gave alkyl 3-acyl-5,6-dicyanobenzofuran-2-carboxylates, 4-(2-R-2-oxoethyl)-5-nitrophthalonitriles, or 3-acyl-1,2-benzoxazole-5,6-dicarbonitriles. With a base, 4-(2-R-2-oxoethyl)-5-nitrophthalonitriles either undergo nitro-nitrite rearrangement resulting in 3-acyl-1,2-benzoxazole-5,6-dicarbonitriles or yield 2-R-benzofuran-5,6-dicarbonitriles with a nitro group displacement.

Chlorination of 2-aryl-1-hydroxyindole-5,6-dicarbonitriles with N-chlorosuccinimide affords previously unknown 3,3-dichloro-3H-indole 1-oxides instead of the expected 1-hydroxy- 3-chloroindoles. The latter can be prepared in good yields by treatment of the above 3,3-dichloro-3H-indole 1-oxides with piperidine in ethanol.

The principal method for the preparation of substituted 4-formyl-1H-pyrazoles was the treatment of hydrazones of different structure with Vilsmeier-Haack reagent. However, for the heterocyclic benzofuran system this reaction is rarely used. Synthetic methods for preparation of novel substituted 3-(4-fomyl-1H-pyrazole-3-yl)-2-methylbenzofuran-5,6-dicarbonitriles and 2-(1H-pyrazole-4-yl)-benzofuran-5,6-dicarbonitriles were developed by modification of 2,3-disubstituted benzofuran-5,6-dicarbonitriles via Vilsmeier-Haack reaction. New substituted 3-(4-fomyl-1H-pyrazole-3-yl)-2-methylbenzofuran-5,6-dicarbonitriles were obtained by reacting 3-acetyl-2-methyl-1-benzofuran-5,6-dicarbonitrile with hydrochloric substituted phenylhydrazines followed by treatment with the Vilsmeier reagent formed hydrazones. A new method for the synthesis of 3-substituted 2-(1H-pyrazol-4-yl)-benzofuran-5,6-dicarbonitriles was based on condensation of aminovinylbenzofuranes with hydrazine hydrate in refluxing acetic acid. The structure of synthesized compounds was determined by data of the IR and NMR spectroscopy, including two-dimensional correlation 1H-1H spectroscopy, and mass spectrometry. The signals of cyano and formyl groups were characteristic in IR spectra; the signals of phthalonitrile protons and proton of aldehyde group - in 1H NMR spectra for 3-(4-formyl-1H-pyrazole)-2-methyl-1-benzofuran-5,6-dicarbonitriles. Also, structure of synthesized 4-formylpyrazoles is confirmed by their reaction with hydrazine hydrate to give corresponding hydrazones. The signals of NH-pronon of pyrazole ring, cyano and carbonyl groups were characteristic in IR spectra; signal broadened singlet of NH-proton of pyrazole ring, which determined to prototropic ring tautomerism of pyrazole ring, and singlets of phthalonitrile protons - in 1H NMR spectra for 3-substituted 2-(1H-pyrazol-4-yl)-benzofuran-5,6-dicarbonitriles. Development of methods for the synthesis of new 4-formylpyrazoles is an important task because the compounds exhibit various pharmacological properties: antimicrobial, anti-inflammatory, antituberculosis, antitumoral, antiparasitic, and antiviral.Forcitation:Chirkova Zh.V., Filimonov S.I., Abramov I.G. Synthesis of benzofuran-5,6-dicarbonitriles annelated with pyrazole cycle. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 6. P. 45-51.

В данном обзоре рассмотрены основные синтетические подходы для получения N-гидроксииндолов. Первый подход заключается во внутримолекулярной восстановительной циклизации орто-замещенных нитроароматических соединений различными химическими восстановителями. В качестве субстратов для синтеза N-гидроксииндолов используются 2-нитрофенилацетальдегиды (синтез по Ачесону), N,N-дизамещенные амино-2-нитростиролы (синтез по Сомею), орто-нитрокетоэфиры различного строения или 1-(o-нитроарил)-1-цианоалкены, орто-нитрокетоны, орто-нитрофенилацетонитрилы. В качестве восстановителей применяются треххлористый титан, цинк либо в присутствии хлористого аммония, либо в уксусной кислоте, двухлористое олово, а также водород с использованием катализаторов на основе благородных металлов (платина, палладий). Вторым подходом является [3+2]-циклоприсоединение нитрозоароматических соединений к алкинам или дезоксигенирование орто-замещенных нитроароматических соединений с последующей внутримолекулярной циклизацией. Третий подход представляет собой каталитическое окисление 2,3-дигидроиндолов или индолов различного строения концентрированной перекисью водорода в присутствии каталитических количеств вольфрамата натрия. Особое внимание уделено синтезу функциональных производных N-гидроксииндол-5,6-дикарбоновых кислот. Это обусловлено тем, что данные соединения, как правило, синтезируют из коммерчески доступного сырья без использования дорогостоящих катализаторов, применяя хорошо известные и отработанные методы синтеза. При этом удалось получать индолы различного дизайна, которые, например, могут являться основными билдинг-блоками для синтеза БАВ, фталоцианинов различного строения, обладающих жидкокристаллическими и каталитическими свойствами. Представители этого класса гетероциклов встречаются среди многочисленных природных соединений, могут быть использованы в качестве терапевтических агентов, например, как ингибиторы человеческой лактатдегидрогеназы изоформы 5, селективные ингибиторы моноаминооксидазы А и Б, а N-метоксииндолы могут применяться для лечения рака молочной железы. Для цитирования: Чиркова Ж.В. Синтез N -гидроксииндолов. Изв. вузов. Химия и хим. технология . 2017. Т. 60. Вып. 4. С. 4-20.

New 5,6-dicyanobenzofurans bearing a 2-(thi)oxotetrahydropyrimidine moiety at the 2-position were synthesized from 2-(2-dimethylaminovinyl)-5,6-dicyanobenzofurans, benzaldehydes and (thio)urea in AcOH.

A new stereoselective method for the synthesis of substituted 5,6-dicyanobenzofurans by activated aromatic nucleophilic replacement of a bromine atom and a nitro group in 4-bromo-5-nitrophthalonitrile has been developed.

Reaction between 4-bromo-5-nitrophthalonitrile and Biginelli pyrimidinethiones affords 7,8-dicyanopyrimido[2,1- b ][1,3]benzothiazoles.

New 5,6-dicyanobenzofurans bearing a 2-(thi)oxotetrahydropyrimidine moiety at the 2-position were synthesized from 2-(2-dimethylaminovinyl)-5,6-dicyanobenzofurans, benzaldehydes and (thio)urea in AcOH.

A new stereoselective method for the synthesis of substituted 5,6-dicyanobenzofurans by activated aromatic nucleophilic replacement of a bromine atom and a nitro group in 4-bromo-5-nitrophthalonitrile has been developed.