Cycloaddition reactions of heterocyclic azides with 2-cyanoacetamidines as a new route to C,N-diheteroarylcarbamidines

• Pavel S. Silaichev,
• Tetyana V. Beryozkina,
• Vsevolod V. Melekhin,
• Valeriy O. Filimonov,
• Andrey N. Maslivets,
• Vladimir G. Ilkin,
• Wim Dehaen and
• Vasiliy A. Bakulev

Beilstein J. Org. Chem. 2024, 20, 17–24, doi:10.3762/bjoc.20.3

• and Molecules, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium 10.3762/bjoc.20.3 Abstract A novel and efficient base-catalyzed, transition-metal-free method for the synthesis of diheterocyclic compounds connected by an amidine linker, including apart from the common

• comprising pyrimidine and 1,2,3-triazole rings connected with an amidine linker by the cycloaddition reaction of 3,3-diaminoacrylonitriles with 6-azidopyrimidine (Scheme 1C). Based on this idea, an efficient and novel method with wide scope has been developed which was then applied to obtain a variety of

• -diaminoacrylonitriles 1 with heteroaryl azides (HetN3) 2 [16] leading to 5-amino-1,2,3-triazole-4-N-heteroarylcarbimidamides 3 (Scheme 1C). Results and Discussion Optimization of the reaction of amidine 1a with azide 2a We initiated the study by investigating a model reaction involving the cycloaddition of 3-amino-3

1-Butyl-3-methylimidazolium tetrafluoroborate as suitable solvent for BF₃: the case of alkyne hydration. Chemistry vs electrochemistry

• Marta David,
• Elisa Galli,
• Richard C. D. Brown,
• Marta Feroci,
• Fabrizio Vetica and
• Martina Bortolami

Beilstein J. Org. Chem. 2023, 19, 1966–1981, doi:10.3762/bjoc.19.147

• analysis (amidine carbon atom at 161.6 ppm in BMIm-BF4, taking as internal reference the imidazolium C2 at 136.4 ppm) [116]. The addition of an excess of BF3·Et2O to the solution of DBU in IL shifted the DBU amidine signal to 166.0 ppm, confirming the rapid formation of the adduct (see Supporting

Trifluoromethylated hydrazones and acylhydrazones as potent nitrogen-containing fluorinated building blocks

• Zhang Dongxu

Beilstein J. Org. Chem. 2023, 19, 1741–1754, doi:10.3762/bjoc.19.127

• trifluoromethylated 1,2,4-triazoles were synthesized with excellent regioselectivities in [3 + 2] cycloaddition reactions of trifluoromethylated hydrazonoyl chlorides with imidates, amidine and 1H-benzo[d]imidazole-2-thiols, all of which were individually reported by Wang, Deng and Cai, respectively [77][78][79

Synthesis, α-mannosidase inhibition studies and molecular modeling of 1,4-imino-ᴅ-lyxitols and their C-5-altered N-arylalkyl derivatives

• Martin Kalník,
• Sergej Šesták,
• Juraj Kóňa,
• Maroš Bella and
• Monika Poláková

Beilstein J. Org. Chem. 2023, 19, 282–293, doi:10.3762/bjoc.19.24

• endocyclic nitrogen with a benzyl or alkyl unit functionalized either with non-polar hydrocarbons or a polar amine, amidine and guanidine group. The ensuing assay with the model GMIIb enzyme (fruit fly Golgi α-mannosidase II) revealed that N-substitution improved both potency and selectivity, achieving

• (AMAN-2) (GH38 family, E.C.3.2.1.114) was included in the biochemical assay as its active site is more similar to human GMII than that of GMIIb. The resulting biochemical evaluation revealed that imino-ᴅ-lyxitols with N-substituents possessing a polar basic functional group (amidine or guanidine) were 6

Cs₂CO₃-Promoted reaction of tertiary bromopropargylic alcohols and phenols in DMF: a novel approach to α-phenoxyketones

• Ol'ga G. Volostnykh,
• Olesya A. Shemyakina,
• Anton V. Stepanov and
• Igor' A. Ushakov

Beilstein J. Org. Chem. 2022, 18, 420–428, doi:10.3762/bjoc.18.44

• )pyrroles [15]. The CsF-promoted nucleophilic addition of isocyanides to bromoacetylenes furnished the functionalized bromovinyl amides followed by Pd-catalyzed formation of 5-iminopyrrolone [16]. Sequential nucleophilic addition/intramolecular cyclization of amidine with bromoacetylenes led to imidazoles

Synthesis of novel [1,2,4]triazolo[1,5-b][1,2,4,5]tetrazines and investigation of their fungistatic activity

• Anna V. Korotina,
• Svetlana G. Tolshchina,
• Rashida I. Ishmetova,
• Natalya P. Evstigneeva,
• Natalya A. Gerasimova,
• Natalya V. Zilberberg,
• Nikolay V. Kungurov,
• Gennady L. Rusinov,
• Oleg N. Chupakhin and
• Valery N. Charushin

Beilstein J. Org. Chem. 2022, 18, 243–250, doi:10.3762/bjoc.18.29

• -disubstituted 1,2,4,5-tetrazines bearing amidine fragments. It is shown that the heterocyclic systems obtained can be modified easily at C(3) position in the reactions with aliphatic alcohols and amines. Also, the reactivity of [1,2,4]triazolo[1,5-b][1,2,4,5]tetrazines towards CH-active compounds has been

• carried out for the first time. The synthetic approach to new triazolotetrazines involves the preparation of 3,6-disubstituted 1,2,4,5-tetrazines 2a–i bearing the amidine moiety through nucleophilic substitution of the 3,5-dimethylpyrazol fragment in easily available compound 1, followed by oxidative

• of [1,2,4]triazolo[1,5-b][1,2,4,5]tetrazine fragment on antifungal activity of the synthesized compounds, we have tested the activity of their analogues, unannulated 1,2,4,5-tetrazines 2c,g, containing the amidine moiety, and isomeric [1,2,4]triazolo[4,3-b][1,2,4,5]tetrazines. For a comparative

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• simultaneous removal of tert-butyldimethylsilyl and amidine protecting groups, respectively (Scheme 41 and Scheme 42) [26]. The incorporation of the double-headed nucleosides 159 and 163 into oligonucleotides resulted in the formation of thermally stable DNA:RNA duplexes due to an efficient π–π stacking

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• industrialized total synthesis of a nontrivial natural product. The original experimental protocol was recently improved by replacing the inorganic base (KOH, NaOH) with the amidine base diazobicycloundecane (DBU) as well as ethanol with n-propanol [49]. The type-III Guareschi reaction is a three-component

Synthesis of functionalized imidazo[4,5-e]thiazolo[3,2-b]triazines by condensation of imidazo[4,5-e]triazinethiones with DMAD or DEAD and rearrangement to imidazo[4,5-e]thiazolo[2,3-c]triazines

• Alexei N. Izmest’ev,
• Dmitry B. Vinogradov,
• Natalya G. Kolotyrkina,
• Angelina N. Kravchenko and
• Galina A. Gazieva

Beilstein J. Org. Chem. 2021, 17, 1141–1148, doi:10.3762/bjoc.17.87

• -triazine-3-thiones with acetylenedicarboxylic acid dimethyl and diethyl esters (DMAD and DEAD) and subsequent base-catalyzed rearrangement of the obtained imidazo[4,5-e]thiazolo[3,2-b]-1,2,4-triazines into regioisomeric imidazo[4,5-e]thiazolo[2,3-c]-1,2,4-triazine derivatives. Keywords: amidine

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• : amidine; biguanide; guanidine chemistry; metformin derivatives; polynitrogen ligands; synthetic methodology; Introduction Biguanide – or amidinoguanidine – is a chemical compound derived from guanidine in which two guanidine molecules are linked through a common nitrogen atom. Since its first synthesis

• . Addition on N-amidino-amidinopyrazole: The first “bisamidine transfer agent” was developed in 1970 by Schenker and Hasspacher [66] by analogy with the amidine transfer agent N-amidinopyrazole already developed for the conversion of amines to guanidines [67] (Scheme 30). The authors first obtained N-amidino

• within 15 minutes in DMF at 110 °C and 62% yield. Addition on S-methylamidinothiourea: Another possibility to create an “amidine transfer reagent” is to install a thiomethyl leaving group on the bisamidine structure. This can be easily achieved using S-methylguanylisothiourea as already described by

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

• between aldehyde and amidine. The imine G thereby reacts with ethyl cyanoacetate to result in intermediate I, which on intramolecular cyclization leads to D. The remaining pathway pursues same mechanism as the first one (Scheme 27). Later in 2016, Gopalakrishnan and co-workers [74] demonstrated the

• condensation of aromatic aldehydes and heterocyclic ketones followed by a [3 + 3] cycloaddition between A and amidine giving off the intermediate B, which undergoes 1,5-hydrogen transfer followed by 1,3-hydrogen transfer to give the final products (101, Scheme 39). 6.2.4 Imidazo(1,2-a)pyrimidine: The

β-Lactamase inhibition profile of new amidine-substituted diazabicyclooctanes

• Zafar Iqbal,
• Lijuan Zhai,
• Yuanyu Gao,
• Dong Tang,
• Xueqin Ma,
• Jinbo Ji,
• Jian Sun,
• Jingwen Ji,
• Yuanbai Liu,
• Rui Jiang,
• Yangxiu Mu,
• Lili He,
• Haikang Yang and
• Zhixiang Yang

Beilstein J. Org. Chem. 2021, 17, 711–718, doi:10.3762/bjoc.17.60

• -lactamase inhibitors. As part of our efforts, we have synthesized a series of DBO derivatives A1–23 containing amidine substituents at the C2 position of the bicyclic ring. These compounds, alone and in combination with meropenem, were tested against ten bacterial strains for their antibacterial activity in

• MIC from <0.125 mg/L to 2 mg/L, and is comparable to avibactam against both E. coli strains with a MIC value of <0.125 mg/L. Keywords: amidine; antibacterial activity; β-lactamase inhibitors; diazabicyclooctane; synthesis; Introduction Survival stress posed by antimicrobial agents triggers multiple

• utmost necessary to continue the struggle with exploring new inhibitors capable of improved resistance and activity against all classes of β-lactamases. Based on our ongoing efforts towards the synthesis of new DBO-based BLIs, we have synthesized a number of amidine-conjugated derivatives of avibactam

Regioselective synthesis of heterocyclic N-sulfonyl amidines from heteroaromatic thioamides and sulfonyl azides

• Vladimir Ilkin,
• Vera Berseneva,
• Tetyana Beryozkina,
• Tatiana Glukhareva,
• Lidia Dianova,
• Wim Dehaen,
• Eugenia Seliverstova and
• Vasiliy Bakulev

Beilstein J. Org. Chem. 2020, 16, 2937–2947, doi:10.3762/bjoc.16.243

• -arylamino-1,2,3-triazole-4-N-sulfonylcarbimidamides. 2,5-Dithiocarbamoylpyridine reacts with sulfonyl azides to form a pyridine bearing two sulfonyl amidine groups. Keywords: amidines; Dimroth rearrangement; isoxazoles; sulfonyl thiazoles; thioamides; 1,2,3-triazoles; Introduction The biological activity

• interesting building blocks in organic synthesis [17][18][19][20] (Figure 1). An N-sulfonyl amidine was recently found to be a key group in acid–base-induced rearrangements of 1,2,3-triazoles and thiadiazoles [22]. A variety of methods have been developed for the synthesis of N-sulfonyl amidines. The most

• have found that 1-butyl-1,2,3-triazole-4-carbothioamide (1c) reacts well with benzenesulfonyl azide (2c) in various solvents to form the desired 1-butyl-1,2,3-N-sulfonyl amidine 3n in diverse solvents such as n-butanol, n-propanol, toluene, ethanol, water and even under solvent-free conditions (see

Aerobic synthesis of N-sulfonylamidines mediated by N-heterocyclic carbene copper(I) catalysts

• Faïma Lazreg,
• Marie Vasseur,
• Alexandra M. Z. Slawin and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2020, 16, 482–491, doi:10.3762/bjoc.16.43

• , the presence of an N-atom in the amidine structure leads to opportunities as ligands and organocatalysts [6][7][8]. N-Sulfonylamidines and N-sulfonylimidates are members of a specific class of these amidines. One initial methodology developed for the formation of sulfonylamidines was based on the

• through the formation of the corresponding triazolium salt B. The intermediate A can then react with the azide substrate to form a triazolyl–copper complex C. The latter can liberate the amidine product and regenerate either catalyst 6 (triazolium salt B is source of proton) or directly the acetylide

Synthesis of 4-amino-5-fluoropyrimidines and 5-amino-4-fluoropyrazoles from a β-fluoroenolate salt

• Tobias Lucas,
• Jule-Philipp Dietz and
• Till Opatz

Beilstein J. Org. Chem. 2020, 16, 445–450, doi:10.3762/bjoc.16.41

• Tobias Lucas Jule-Philipp Dietz Till Opatz Institute of Organic Chemistry, Johannes Gutenberg-University, Duesbergweg 10–14, 55128 Mainz, Germany 10.3762/bjoc.16.41 Abstract A synthesis of fluorinated pyrimidines under mild conditions from amidine hydrochlorides and the recently described

• . The hydrochlorides furnished the highest yields and no undesired byproducts were formed. In contrast to the related reaction with guanidinium salts [36], the reactions with amidine hydrochlorides did not require any basic additives. Under these improved conditions, the scope of the reaction for

A green, economical synthesis of β-ketonitriles and trifunctionalized building blocks from esters and lactones

• Daniel P. Pienaar,
• Kamogelo R. Butsi,
• Amanda L. Rousseau and
• Dean Brady

Beilstein J. Org. Chem. 2019, 15, 2930–2935, doi:10.3762/bjoc.15.287

• when using sodium amide as the base [5], although the inherent risks of employing explosive sodium amide in synthesis are well known [6] and amidine side-product formation was observed at times through reaction of the nucleophilic amide base with nitrile. Furthermore, clearly two equivalents of base

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• coupling reaction for the synthesis of 2-triazolylimidazo[1,2-a]pyridine 74 (Scheme 26) [31]. The reaction involved the use of copper oxide as a catalyst and sodium ascorbate as a reducing agent using triazolyl aldehyde 73, amidine 3 and terminal alkynes 2 as reaction substrates at 70 °C (Scheme 26). Here

• sodium ascorbate (NaOAs) helped in the reduction of Cu(II) to Cu(I) which then reacted with the alkyne moiety. The species thus formed participated in the reaction by reacting with imine of aldehyde and amidine. The intermediate thus formed undergo 5-exo-dig cyclization and 1,3-H shift to form the final

Mechanochemical synthesis of poly(trimethylene carbonate)s: an example of rate acceleration

• Sora Park and
• Jeung Gon Kim

Beilstein J. Org. Chem. 2019, 15, 963–970, doi:10.3762/bjoc.15.93

• biomedical applications [24]. The amidine base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is one of the best studied and most popular organocatalysts for ring-opening polymerizations of cyclic carbonates and lactones [25][26][27]. In contrast to the high activity of lactone polymerization, cyclic carbonate

An improved synthesis of adefovir and related analogues

• David J. Jones,
• Eileen M. O’Leary and
• Timothy P. O’Sullivan

Beilstein J. Org. Chem. 2019, 15, 801–810, doi:10.3762/bjoc.15.77

• -benzyladenine (25) afforded the corresponding N9-regioisomers as the major product as determined by 1H NMR spectroscopy (Scheme 6a,b). The major isomers were then isolated and subsequently converted to phosphonate 6 in order to confirm the degree of regioselectivity. Interestingly, the amidine moiety in 28

• identification of a correlation between the methylene protons adjacent to the purine ring with C-5. A similar analysis by us revealed the same correlation, confirming 29 as the major product (Figure 4). While the amidine is itself an important moiety in medicinal chemistry [57], it can also be readily converted

• to other functional groups including nitrogen-containing heterocycles [58]. Consequently, the use of the amidine moiety to direct the N7-selective alkylation with iodide 14 may likewise facilitate the preparation of other N7-functionalised adefovir analogues for evaluation. Finally, we investigated

Synthesis of dihydroquinazolines from 2-aminobenzylamine: N³-aryl derivatives with electron-withdrawing groups

• Nadia Gruber,
• Jimena E. Díaz and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2018, 14, 2510–2519, doi:10.3762/bjoc.14.227

• , some ruthenium complexes bearing a 3,4-dihydroquinazoline ligand have been studied as hydrogenation-transfer catalysts, showing good to excellent activity for the reduction of ketones [17]. In the context of our research on heterocyclic amidine N-oxides [18][19][20][21][22], we recently prepared some

• conditions that are incompatible with nitro or cyano groups. In this context, and as part of our ongoing research on heterocyclic amidines (vide infra) and amidine N-oxides we report herein the first method for the synthesis of 2-alkyl/aryl-N-aryl-3,4-DHQs 1 bearing electron-withdrawing groups in the aryl

Selective formation of a zwitterion adduct and bicarbonate salt in the efficient CO₂ fixation by N-benzyl cyclic guanidine under dry and wet conditions

• Yoshiaki Yoshida,
• Naoto Aoyagi and
• Takeshi Endo

Beilstein J. Org. Chem. 2018, 14, 2204–2211, doi:10.3762/bjoc.14.194

• fixation of CO2 such as cycloaddition of CO2 to various epoxides and synthesis of carbonate derivatives from CO2 and alcohols [6][7][8][9][10][11][12][13]. However, these kinds of catalysts often need high temperatures and pressure to completely achieve the CO2 fixation [6]. On the other hand, amidine and

• guanidine derivatives are well known as efficient catalysts for the cycloaddition of CO2 to epoxides at ambient temperature [7][14][15][16][17][18]. Previously, we reported that hydroiodides of amidine derivatives worked as significantly efficient catalysts for the cycloaddition of CO2 to epoxides under

• particular, CO2 capture–release behaviors of bicyclic and six-membered cyclic amidine derivatives have been well studied compared to that of five-membered derivatives, because the high ring strain of five-membered cyclic amidine derivatives was unfavorable for the binding between CO2 and the amidine moiety

Design, synthesis and structure of novel G-2 melamine-based dendrimers incorporating 4-(n-octyloxy)aniline as a peripheral unit

• Cristina Morar,
• Pedro Lameiras,
• Attila Bende,
• Gabriel Katona,
• Emese Gál and
• Mircea Darabantu

Beilstein J. Org. Chem. 2018, 14, 1704–1722, doi:10.3762/bjoc.14.145

• 2008), X. K. Moreno and E. E. Simanek [47] demonstrated the validity of the above TGs in the case of amino-s-triazines, –N(H)–C(=N–)– ↔ –N+(H)=C(–N−–)–, as well, in DMSO-d6. Following this new insight, if the TG values of “amidine-like” protons in amino-s-triazines are more negative than −4 ppb K−1 in

Cobalt-catalyzed C–H cyanations: Insights into the reaction mechanism and the role of London dispersion

• Eric Detmar,
• Valentin Müller,
• Daniel Zell,
• Lutz Ackermann and
• Martin Breugst

Beilstein J. Org. Chem. 2018, 14, 1537–1545, doi:10.3762/bjoc.14.130

• structures resulted in barrierless reactions when a proton approaches the amidine substructure (→ 12a). As the cyanated 2-phenylpyridine 3a is less Lewis-basic compared to the starting material 1a, 12a could also react with 1a in a thermodynamically favorable ligand exchange reaction (ΔG = −2.2 kcal mol−1

Atom-economical group-transfer reactions with hypervalent iodine compounds

• Andreas Boelke,
• Peter Finkbeiner and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2018, 14, 1263–1280, doi:10.3762/bjoc.14.108

• substituted acrylamidines 35 (Scheme 19). The proposed reaction mechanism starts with the activation of DMSO (A) via the iodine(III) species 20b. Iodosoarene C is released under basic conditions, forming the sulfonium intermediate D. This intermediate reacts with the amidine 34 to give the sulfide E, which is

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

• also replaced by various amidine-like groups, such as cyanoamidine, N-methylamidine, N,N-dimethylamidine, and guanidino moieties either to increase the stability, cytotoxicity and enhance solubility at physiological pH. Comparable cytotoxicity was observed in these cases suggesting a general behavior

• of these classes of molecules including the amidine modification. In addition, a novel class of cytotoxic MGBs comprising of α-bromo or chloroacrylamide moieties linked to distamycin were identified. Among all different synthetic analogs, brostacillin (PNU-166196, Figure 3) was found to be a potent

• . Suckling et al. designed a set of 31 Strathclyde minor groove binders (S-MGBs), derived from distamycin, by varying the head groups (amidine, amide, or alkene), heterocyclic building blocks and their alkyl substituents and the basicity of the C-terminal tail group in order to investigate their antimalarial