Synthesis of 4-hydroxy and 6-hydroxyindoles: a renaissance of the Bischler reaction

In the present work we studied a modified Bischler-Möhlau reaction – synthesis of indoles from benzoin and aniline. Our proposed modification of this method differs from that described earlier in that the reaction is carried out at a lower temperature, which makes it possible to improve yields and reduce formation of tarry side products. In addition, unlike the previous contradictory works, which described the preparation of a single 4-hydroxy or 6-hydroxy isomer in condensation of m-aminophenol and benzoin, we obtained both 4-hydroxy and 6-hydroxy isomers

Synthesis of acyclic nucleoside analogues by one-step Vorbrüggen glyco-sylation of 1,2,4-triazolo[1,5-a]pyrimidine-7-ones

New analogues of acyclovir have been prepared by reacting 1,2,4 -triazolo[1,5-a]pyrimidin-7-ones 1а-i and (2-acetoxyethoxy)methyl acetate 2 in the presence of trimethylsilyl trifluoromethanesulfonate as a catalyst. The interaction between the compounds 1а-е and 2 has led to a mixture of N3 and N4 isomers. In contrast, the reaction of compounds 1g-i and 2 proceeded selectively to form N3 isomers. In the case of compounds 1a-c the predominant product is the one with the acyclic moiety in azine ring (N4 isomer). Interaction between 1d-f and 2 has led to mixtures comprising mainly N3 isomer. It has been found that the ratio of glycosylation products 1 and 2 are thermodynamically controlled. The structure of the obtained compounds has been proved by 1Н, 13С, two-dimensional 1Н-13С NMR spectroscopy and X-ray analysis

Direct CH/CH functionalization of 1,3‑dihydroxy-9Hxanthen-9‑one and 1,3‑dimethoxy-9H-xanthen-9‑one with 1,2,4‑triazines and quinazoline

Received: 20.10.2020. Accepted: 19.12.2020. Published:30.12.2020.An electron-deficient series of 1,2,4‑triazines and quinazoline have been used for cross-dehydrogenative coupling with 1,3‑dihydroxy and 1,3‑dimethoxyxanthones to give stable nucleophilic addition products. The adducts and their subsequent oxidation products were obtained in good yields and the structures of the compounds were confirmed by 1H NMR spectroscopy. These results expand the scope of the methodology of nucleophilic substitution of hydrogen with the participation of xanthones with azines. Moreover, this methodology makes it possible to obtain new organic materials based on xanthones, which have a wide spectrum of biological activity.This work was finantionally supported by the Presidential Council on Grants NSh-2700.2020.3 and Ministry of Science and Higher Education of the Russian Federation (project FEUZ-2020-005)

Long-range 1H-15N J couplings providing a method for direct studies of the structure and azide-tetrazole equilibrium in a series of azido-1,2,4-triazines and azidopyrimidines

The selectively 15N labeled azido-1,2,4-triazine 2*A and azidopyrimidine 4*A were synthesized by treating hydrazinoazines with 15N-labeled nitrous acid. The synthesized compounds were studied by 1H, 13C, and 15N NMR spectroscopy in DMSO, TFA, and DMSO/TFA solutions, where the azide-tetrazole equilibrium could lead to the formation of two tetrazoles (T, T′) and one azide (A) isomer for each compound. The incorporation of the 15N label led to the appearance of long-range 1H-15N coupling constants (JHN), which can be measured easily by using amplitude-modulated 1D 1H spin-echo experiments with selective inversion of the 15N nuclei. The observed JHN patterns enable the unambiguous determination of the mode of fusion between the azole and azine rings in the two groups of tetrazole isomers (2*T′, 4*T′ and 2*T, 4*T), even for minor isoforms with a low concentration in solution. However, the azide isomers (2*A and 4*A) are characterized by the absence of detectable J HN coupling. The analysis of the JHN couplings in 15N-labeled compounds provides a simple and efficient method for direct NMR studies of the azide-tetrazole equilibrium in solution. © 2013 American Chemical Society

Spin-spin coupling constants 13C-15N and 1H-15N in the investigation of azido-tetrazole tautomerism in a series of 2-azidopyrimidines

A new method was developed for the investigation of an azido-tetrazole equilibrium based on using a complex analysis of 13C-15N and 1H-15N spin-spin coupling constants. The use of this approach became possible due to the selective inclusion of 15N isotopes into the structures of 2-azidopyrimidines and their cyclic analogs tetrazolo[1,5-a]pyrimidines. © 2013 Springer Science+Business Media New York

NUCLEOPHILIC SUBSTITUTION OF HYDROGEN IN ANNULATED DIAZINES UNDER THE ACTION OF 7-AMINOCOUMARINS

Работа выполнена при поддержке фонда РНФ, проект № 21-73-00214

Unusual nicotinoylation of 4-phenyl-5,7-dihydroxycoumarin

Received: 18.11.2021. Revised: 21.12.2021. Accepted: 21.01.2022. Available online: 26.01.2022.The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.In the present work, we report a convenient synthesis of 5- and 7-substituted-4-phenyl coumarins. In contrast to previous results obtained with 4-alkylcoumarins, nicotinoylation of 5,7-dihydroxy-4- phenylcoumarin with nicotinoyl benzotriazole or nicotinoyl azide selectively provides 5-O protected ester. The combination of the nicotinoylation reaction followed by tosylation-denicotinoylation yields 5-hydroxy-7-tosyloxy-coumarin derivative, which may be useful in the synthesis of inophyllum, a tetracyclic HIV reverse transcriptase inhibitor, as well as its analogues.This work is financially supported by Russian Science Foundation (Ref No. 21-13-00382)

Benzo[de]naphtho[1,8-gh]quinolines: synthesis, photophysical studies and nitro explosives detection

A rational synthetic approach to substituted naphtho[1,8-gh]quinolines using intramolecular cyclization in the presence of potassium in the series of (naphthalen-1-yl)isoquinolines is described. The photophysical properties of the obtained compounds were studied; in particular, fluorescence emission was detected in the range 454 - 482 nm with a quantum yield of up to 54%. We also calculated the HOMO-LUMO energies and optimized molecular structures for the resulting fluorophores. Based on the results of fluorescence titration, the Stern-Volmer constants (up to 21587 M-1) and the detection limits of nitroanalytes (up to 1.4 ppm) were calculated, confirming the possibility of their use as potential chemosensors for the visual detection of nitro-containing explosives

Unlocking training and skills development for sustainability in small and medium enterprises (SMEs) : an explorative South African study

This qualitative study explored and described the role and contribution of training and skills development for sustainability in SMEs in the manufacturing sector in Durban and East London, South Africa. Individual face-to-face semi-structured interviews took place with 15 SME owners. Five themes and 11 sub-themes emerged in a content thematic analysis. The findings indicate that SMEs acknowledge that training and skills development positively influences their financial performance and sustainability. Whilst SMEs implement learning and skills development interventions, they lack suitably structured human resource development (HRD) policies and strategies; do not properly document training and skills development activities; and experience difficulty in evaluating learning. This study recommends that SMEs formulate and implement well-structured learning and development plans and schedules. It is also advised that SMEs liaise with academics and form Communities of Practice (CoPs), among other initiatives, to implement and monitor training and skills development for their sustainability.Business ManagementM. Com. (Business Management

Combination of NH2OHHCl and NaIO4: A new and mild reagent for the synthesis of vicinal diiodo carbonyl compounds

The synthesis of vicinal diiodo carbonyl compounds from α,β-unsaturated carbonyl compounds has been carried out for the first time using the combination of NH2OHHCl and NaIO4 under mild reaction conditions at room temperature. The present methodology is also applicable for the synthesis of vicinal diiodo derivatives of nitrostyrene. The remarkable advantages of the present protocol are room temperature reaction, easy operation, good yields, fast reaction, transition metal-free and neutral reaction conditions. The present methodology is applicable to gram scale synthesis. © 2016 Arkat. All rights reserved