Hypervalent iodine-mediated intramolecular alkene halocyclisation

• Charu Bansal,
• Oliver Ruggles,
• Albert C. Rowett and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 3113–3133, doi:10.3762/bjoc.20.258

• nitrogen forms the cyclised intermediate and a chloride ion displaces iodobenzene. In 2015, Cariou, Dodd and co-workers reported the synthesis of chlorinated cyclic guanidines 44 (Scheme 24) [47]. Using Koser’s reagent as an oxidant with LiCl as a source of chloride, a range of unsaturated guanidines 43

• guanidines 61 (Scheme 33) alongside their chlorinated cyclic guanidines 44 (vide supra) [47]. Koser’s reagent was employed with LiBr to form 5- and 6-membered brominated cyclic guanidines 61 and 61’ in good yields from allylic guanidines 43. A range of substrates with substituents on the terminal alkene were

• source of fluoride and an activating reagent. Intramolecular carbofluorination of alkenes. Intramolecular chlorocyclisation of unsaturated amines. Synthesis of chlorinated cyclic guanidines 44. Synthesis of chlorinated pyrido[2,3-b]indoles 46. Chlorolactonization and chloroetherification reactions

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• ) [92]. Besides α-fluoro-β-ketoamides, α-chloro-substituted ketoamide was also tolerated well in this transformation. Screening several chiral guanidines as the bifunctional catalyst revealed that these organocatalysts were suitable for the synthesis of α-fluoro/chloro-α-sulfenyl-β-ketoamides 144 and

Complementarity of solution and solid state mechanochemical reaction conditions demonstrated by 1,2-debromination of tricyclic imides

• Petar Štrbac and
• Davor Margetić

Beilstein J. Org. Chem. 2022, 18, 746–753, doi:10.3762/bjoc.18.75

• , Cycloaddition strategies towards polycyclic guanidines (CycloGu)). Poster presented at the ACS 25th Annual Green Chemistry & Engineering Conference, June 14-18, 2021.

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

• (ii) from guanidines. The main approaches that have been developed for the synthesis of biguanides so far are summarized in Figure 3. Globally, these two groups can be further divided into eight main procedures: four starting from amines (Figure 3, routes a–d) and four from guanidines (Figure 3

• cyanoguanidines, dicyanamides, carbamide or N1-cyano-S-methylisothioureas and the addition of guanidines to carbodiimides, cyanamides or (iso)(thio)urea derivatives. Synthesis from amines Addition of amines to cyanoguanidines (pathway a) Reaction of amines with cyanoguanidine: The use of cyanoguanidine as the

• . 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

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• -bond adduct. The first light-promoted three-component reaction has been realized by a halogen-bond adduct, forming perfluoroalkylated pyrimidines 26 (Scheme 8). A variety of perfluorinated chains were assembled with methylene compounds and guanidines or amidines, giving the corresponding

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

• ambient temperature and pressure [19][20][21][22]. Furthermore, cyclic amidines and guanidines, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), exhibited an excellent efficiency of CO2 capture and release [23][24][25][26][27][28][29][30][31][32][33]. In

• a low magnetic field, because the electrons on bicarbonate and guanidinium carbons were delocalized on oxygen and nitrogen atoms by their resonance effect, respectively. Previously, some researchers have reported similar assignments for zwitterion adducts of amidines and guanidines [29][30][31]. The

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• carbamates [92], sulfamates [94][95][96][97], ureas and guanidines [98], sulfamides [99], hydroxylamine-derived sulfamates [100], carbamimidates [101], and sulfonimidamides [102][103][104][105][106][107]. These reactions involve the formation of a metal-bound nitrene that can insert into a C(sp3)–H bond or a

Synthesis of chiral 3-substituted 3-amino-2-oxindoles through enantioselective catalytic nucleophilic additions to isatin imines

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 1349–1369, doi:10.3762/bjoc.14.114

• reactions performed with bifunctional guanidines. In addition, excellent results (97% ee) were reported in unprecedented domino reactions promoted by squaramides recently. Miscellaneous transformations, including additions of methanol, hydroperoxides and arylboronic acids, were also developed with high

Oligonucleotide analogues with cationic backbone linkages

• Melissa Meng and
• Christian Ducho

Beilstein J. Org. Chem. 2018, 14, 1293–1308, doi:10.3762/bjoc.14.111

• triplex formation was enhanced for all tested RP congeners. The aminoalkylation generally provided an increased nuclease stability, which was more pronounced for the RP isomers. Deoxyribonucleic guanidines (DNG) with guanidinium linkages In their design of cationic oligonucleotide analogues, Bruice et al

• . did not just attach a cationic moiety to the modified phosphate diester backbone, but they completely replaced it with a guanidinium linkage to give 'deoxyribonucleic guanidines (DNG)' of type 8 [49]. The guanidinium group was selected owing to its maintenance of a positive charge over a broad pH

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

Phosphodiester models for cleavage of nucleic acids

• Satu Mikkola,
• Tuomas Lönnberg and
• Harri Lönnberg

Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68

• as RNA model and the reactions were carried out in 80% aq DMSO. On using a bis(guanidine)-substituted compound as a catalyst, the maximal cleavage rate was observed at pH 10.4, where only one of the two guanidines was protonated. The 1,3-distal isomer was twice as effective as its 1,2-vicinal

Mechanochemical synthesis of thioureas, ureas and guanidines

• Vjekoslav Štrukil

Beilstein J. Org. Chem. 2017, 13, 1828–1849, doi:10.3762/bjoc.13.178

• Vjekoslav Strukil Division of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia 10.3762/bjoc.13.178 Abstract In this review, the recent progress in the synthesis of ureas, thioureas and guanidines by solid-state mechanochemical ball milling is

• enabled the quantitative synthesis of (thio)ureas and guanidines without using bulk solvents and the generation of byproducts, but it has also been established as a means to develop "click-type" chemistry for these classes of compounds and the concept of small molecule desymmetrization. Moreover

• application as organocatalysts and sensors. On the other hand, the specific and unique nature of each of these functionalities render (thio)ureas and guanidines as the key constituents of pharmaceuticals and other biologically active compounds. Keywords: guanidines; mechanochemistry; solid state synthesis

Derivatives of the triaminoguanidinium ion, 5. Acylation of triaminoguanidines leading to symmetrical tris(acylamino)guanidines and mesoionic 1,2,4-triazolium-3-aminides

• Jan Szabo,
• Julian Greiner and
• Gerhard Maas

Beilstein J. Org. Chem. 2017, 13, 579–588, doi:10.3762/bjoc.13.57

• either symmetrical N,N’,N’’-tris(N-acyl-N-benzylamido)guanidines 6 or mesoionic 4-amino-1,2,4-triazolium-3-hydrazinides 7. The latter were converted into 1,2,4-triazolium salts by protonation or methylation at the hydrazinide nitrogen atom. Neutral 1,2,4-triazoles 10 were obtained by catalytic

• hydrogenation of an N-benzyl derivative. Crystal structure analyses of a 4-benzylamino-1,2,4-triazolium-3-hydrazinide and of two derived 1,2,4-triazolium salts are presented. Keywords: guanidines; mesoionic compounds; triaminoguanidinium salts; 1,2,4-triazolium-3-aminides; Introduction Easily accessible by

• , triaminoguanidinium salts or the neutral triaminoguanidine have been reacted with carbonyl compounds. Reactions with aldehydes [3][4][5][6][7] or ketones [8][9][10] yielded the corresponding tris(iminyl)guanidines; cyclocondensation of pentane-2,4-dione at one hydrazinyl branch of TAG-Cl afforded a pyrazole which

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• [50][51]. In 2013 Bibal and co-workers investigated the use of methylated amines, pyridines and guanidines (L11) as hydrogen bond-donor catalysts for the activation of cyclic esters toward ring-opening polymerization (ROP) [53]. Ionic catalysts L11 (5 mol %) were successfully employed in combination

Enduracididine, a rare amino acid component of peptide antibiotics: Natural products and synthesis

• Darcy J. Atkinson,
• Briar J. Naysmith,
• Daniel P. Furkert and
• Margaret A. Brimble

Beilstein J. Org. Chem. 2016, 12, 2325–2342, doi:10.3762/bjoc.12.226

• cyclic guanidines 51 and 52 was initiated through cleavage of the N,O-acetonide and guanylation using isothiourea 33 activated with HgCl2 (Scheme 8). Cyclisation of the guanidine afforded protected β-hydroxyenduracididine 51 in 21% yield in seven steps from diol 49. The C-2 epimer 47 was converted to β

• sulfonamide 56 in 56% yield as a 1:1 mixture of diastereomers (Scheme 10). Selective deprotection of the sulfonamide Boc group allowed separation of diastereomers 57 and 58 via chromatography which were then converted to Tces (2,2,2-trichloroethoxysulfonyl) protected guanidines 59 and 60. Global deprotection

A chiral analog of the bicyclic guanidine TBD: synthesis, structure and Brønsted base catalysis

• Mariano Goldberg,
• Denis Sartakov,
• Jan W. Bats,
• Michael Bolte and
• Michael W. Göbel

Beilstein J. Org. Chem. 2016, 12, 1870–1876, doi:10.3762/bjoc.12.176

• chemical correlation. Keywords: absolute configuration; anthrone; cycloaddition; kinetic resolution; lipase; Introduction In guanidinium ions charge delocalization is an important factor to stabilize the protonated form. As a result, guanidines are exceptionally strong nitrogen bases. As part of the

• amino acid arginine, they play an important role in biochemistry, mainly by forming ion pairs. In addition, numerous guanidine derivatives with complex cyclic structures can be found in natural products [1]. Simple guanidines such as tetramethylguanidine have been used as strong Brønsted bases in

• natural products, have been used as chiral phase-transfer catalysts [12][13]. Bicyclic guanidines with five-membered rings are also known from the alkaloid isoalchornein [14][15]. In subsequent years, synthetic compounds (6–9) of this structural type have been developed as chiral Brønsted bases [16][17

Sequence-specific RNA cleavage by PNA conjugates of the metal-free artificial ribonuclease tris(2-aminobenzimidazole)

• Friederike Danneberg,
• Alice Ghidini,
• Plamena Dogandzhiyski,
• Elisabeth Kalden,
• Roger Strömberg and
• Michael W. Göbel

Beilstein J. Org. Chem. 2015, 11, 493–498, doi:10.3762/bjoc.11.55

• . Here we report a new and mercury-free synthesis of tris(2-aminobenzimidazole) and its conjugation to PNA oligomers. In addition, the results of cleaving experiments with three different RNA substrates are presented. Results and Discussion Alternative reagents to convert thioureas into guanidines

• include metal salts like CuCl2 or HgCl2 and carbodiimides such as 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDCI) or N,N’-diisopropylcarbodiimide (DIC) [17]. Another method developed by Lipton et al. uses Mukaiyama's reagent (2-chloro-1-methylpyridinium iodide) to prepare guanidines in high yields

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• mutagenic activities) compared with ethidium bromide. A recent study showed that substitution of both ethidium bromide (EB) and exocyclic amines by guanidines converted the classical intercalator (EB) into a DNA minor groove binder [57]. The most intriguingly, binding mode change did not weaken the DNA

Derivatives of the triaminoguanidinium ion, 3. Multiple N-functionalization of the triaminoguanidinium ion with isocyanates and isothiocyanates

• Jan Szabo,
• Kerstin Karger,
• Nicolas Bucher and
• Gerhard Maas

Beilstein J. Org. Chem. 2014, 10, 2255–2262, doi:10.3762/bjoc.10.234

• . Molecular architectures of this kind could be useful under several aspects, for example in biologically active compounds, as novel ligands in metal complexes, for the construction of dendrimers, and in crystal engineering. Along these lines, several 1,2,3-tris(iminyl)guanidines have been prepared from

• triaminoguanidinium chloride (1, TAG-Cl) and salicylaldehyde, ring-substitued derivatives thereof [2][3][4][5] and 3-(hydroxyimino)pentane-2,4-dione [6] to prepare 1,2,3-tris(iminyl)guanidines; as multidentate chelating ligands they form complexes with several metal ions giving rise to various supramolecular

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• ], phenylacetylene [73][74], and methyl acrylate [75]. Starting from these results, a MC approach to 1-(isoquinolin-1-yl)guanidines 55 was efficiently developed by a silver triflate-catalyzed three-component reaction of 2-alkynylbenzaldehydes 25, tosylhydrazide (41) and carbodiimides 54 (Scheme 29) [76]. The

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

Organocatalyzed enantioselective desymmetrization of aziridines and epoxides

• Ping-An Wang

Beilstein J. Org. Chem. 2013, 9, 1677–1695, doi:10.3762/bjoc.9.192

• including cinchona alkaloid derivatives, chiral phosphoric acids, chiral amino alcohols, chiral thioureas, chiral guanidines, and chiral 1,2,3-triazolium chlorides. In this review, the research work of enantioselective desymmetrization of meso-aziridines is organized into sections according to the employed

• give the corresponding β-chlorobenzamides in high yields and enantioselectivities. Chiral guanidines Tan [51] and co-workers developed a series of chiral guanidines based on an amino indanol backbone (Figure 9, OC-45 to OC-48), which proved to be very efficient organocatalysts for the enantioselective

• -aziridines are plentiful and can be found in a diverse set of privileged structures, including cinchona alkaloids-based PTCs, L-proline-derived amino alcohols, chiral phosphorous acids, chiral thioureas, chiral guanidines, and chiral 1,2,3-triazolium chlorides. But for the desymmetrization of meso-epoxides

The rapid generation of isothiocyanates in flow

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 1613–1619, doi:10.3762/bjoc.9.184

• isocyanides [30][31], guanidines [32][33] and thiosemicarbazides [34]. Due to the limited commercial availability of diversely functionalised isothiocyanates chemists normally pursue a de novo synthesis, which most commonly involves the condensation of an amine with thiophosgene or carbon disulfide [35][36

Isolation and X-ray characterization of palladium–N complexes in the guanylation of aromatic amines. Mechanistic implications

• Abdessamad Grirrane,
• Hermenegildo Garcia and
• Eleuterio Álvarez

Beilstein J. Org. Chem. 2013, 9, 1455–1462, doi:10.3762/bjoc.9.165

• guanidines are commercially used as antifouling agents in marine paints and in the formulation of protective surface coatings [8][9][10]. N-Arylguanidines can be obtained by aniline insertion into the corresponding carbodiimide [11][12][13][14][15][16][17][18]. This nucleophilic addition can be efficiently

• precipitates were observed. In contrast, in the presence of catalytic amounts of palladium, formation of the corresponding N-arylguanidines was observed in almost quantitative yield. These guanidines 5a–c formed by nucleophilic attack of anilines 1a–c to N,N’-diisopropylcarbodiimide (2) catalyzed by palladium

• also Supporting Information File 1, Table S4 and Figure S20 and for full details of crystallographic data see Supporting Information File 2). Beside X-ray crystal analysis of guanidine 5a, guanidines 5a–c were also characterized by 1H, 13C and 19F NMR spectroscopy and combustion analysis (see Figures

Thiourea-catalyzed Diels–Alder reaction of a naphthoquinone monoketal dienophile

• Carsten S. Kramer and
• Stefan Bräse

Beilstein J. Org. Chem. 2013, 9, 1414–1418, doi:10.3762/bjoc.9.158

• carbenes, guanidines, thioureas, amidinium ions, diols, and Brønsted acids showed their value to give densely functionalized Diels–Alder products in high selectivities [1][2][3][4][5][6][7]. In addition, some organocatalysts enabled even the formation of quaternary centers in Diels–Alder cycloadditions [3