Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

• were removed with hydrazine under reflux and the free amino groups were acetylated to obtain the fully N-acetylated COS [255]. Control over the pattern of N-acetylation was for the first time achieved using two monosaccharides bearing an azido (N3) and a N-Phth moieties as precursors of the free and N

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

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

Hydrazides in the reaction with hydroxypyrrolines: less nucleophilicity – more diversity

• Dmitrii A. Shabalin,
• Evgeniya E. Ivanova,
• Igor A. Ushakov,
• Elena Yu. Schmidt and
• Boris A. Trofimov

Beilstein J. Org. Chem. 2021, 17, 319–324, doi:10.3762/bjoc.17.29

• emphasis on the nature of hydrazine derivatives still remains obscure. Meeting this challenge becomes particularly important in view of the significance of the less nucleophilic hydrazides as N–N-bond containing starting materials in drug discovery [13][14][15][16]. Herein, we report how a lower

• formation of 1,4-dihydropyridazine 4. Conclusion In summary, an acid-catalyzed recyclization of hydroxypyrrolines (easily synthesized from ketoximes and acetylene) with hydrazides was studied. The reduced nucleophilicity of the hydrazides in comparison with other hydrazine derivatives constitutes the basis

• . Recyclization of hydroxypyrrolines with hydrazine derivatives. Synthesis of tetrahydropyridazines 3. Synthesis of dihydropyridazines 4. Recyclization of hydroxypyrroline 1a with hydrazides 2d and 2e. A proposed mechanism for the recyclization of hydroxypyrrolines 1 with hydrazides 2. A study of the model

Synthesis of imidazo[1,5-a]pyridines via cyclocondensation of 2-(aminomethyl)pyridines with electrophilically activated nitroalkanes

• Dmitrii A. Aksenov,
• Nikolai A. Arutiunov,
• Vladimir V. Maliuga,
• Alexander V. Aksenov and
• Michael Rubin

Beilstein J. Org. Chem. 2020, 16, 2903–2910, doi:10.3762/bjoc.16.239

• colorless crystals of intermediate 2-((6-bromoquinolin-2-yl)methyl)isoindoline-1,3-dione. This material (3.05 g, 8.3 mmol) was suspended in ethanol, and hydrazine hydrate (50%, 1.0 g, 10 mmol) was added. The reaction mixture was refluxed for 5 h and then cooled down to 0 °C. The precipitated phthalyl

Nocarimidazoles C and D, antimicrobial alkanoylimidazoles from a coral-derived actinomycete Kocuria sp.: application of ¹J_C,H coupling constants for the unequivocal determination of substituted imidazoles and stereochemical diversity of anteisoalkyl chains in microbial metabolites

• Md. Rokon Ul Karim,
• Enjuro Harunari,
• Amit Raj Sharma,
• Naoya Oku,
• Kazuaki Akasaka,
• Daisuke Urabe,
• Mada Triandala Sibero and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 2719–2727, doi:10.3762/bjoc.16.222

• with 1-chloropropan-2-one to give 3-acetylimidazo[1,2-a]pyrimidine, which, following degradation of the pyridimine ring with hydrazine, yielded 9. The coupled HSQC experiments measured 1JC,H = 215 Hz for the H-2/C-2 pair in 8 (Figure S26, Supporting Information File 1) and 201 Hz for H-5/C-5 in 9

Design and synthesis of a bis-macrocyclic host and guests as building blocks for small molecular knots

• Elizabeth A. Margolis,
• Rebecca J. Keyes,
• Stephen D. Lockey IV and
• Edward E. Fenlon

Beilstein J. Org. Chem. 2020, 16, 2314–2321, doi:10.3762/bjoc.16.192

• bromide in 1-bromo-4-chlorobutane (16) with sodium azide to give azide 17 in 52% yield (Scheme 5). Treatment of 17 with potassium phthalimide and catalytic potassium iodide was followed by hydrazine unmasking to give the desired aminoazide 18 in 37% over the two steps. Reductive amination of 18 with dial

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• the chemistry of the sumanene and its congeners, quite recently the same group has also prepared sumanene-based carbene 60 starting from monosumanenone 38 by reacting it with hydrazine hydrate to provide the corresponding hydrazone 58 which on further oxidation with MnO2 followed by irradiation using

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

Efficient [(NHC)Au(NTf₂)]-catalyzed hydrohydrazidation of terminal and internal alkynes

• Maximillian Heidrich and
• Herbert Plenio

Beilstein J. Org. Chem. 2020, 16, 2080–2086, doi:10.3762/bjoc.16.175

• (Scheme 1) [7] such as water or alcohol [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], primary or secondary amines [23][24][25][26][27][28], or hydrazine [29][30][31]. These reactions are synthetically useful since gold catalysis is characterized by a good functional group tolerance for

Synthesis of monophosphorylated lipid A precursors using 2-naphthylmethyl ether as a protecting group

• Jundi Xue,
• Ziyi Han,
• Gen Li,
• Khalisha A. Emmanuel,
• Cynthia L. McManus,
• Qiang Sui,
• Dongmian Ge,
• Qi Gao and
• Li Cai

Beilstein J. Org. Chem. 2020, 16, 1955–1962, doi:10.3762/bjoc.16.162

• ) group under basic conditions followed by peracetylation afforded compound 10 on a ≈150 g scale. The regioselective anomeric deacetylation with hydrazine and reprotection of the anomeric hydroxy group as tert-butyldimethylsilyl ether (TBS) led to compound 12. Compound 12 was then treated with sodium

Tuneable access to indole, indolone, and cinnoline derivatives from a common 1,4-diketone Michael acceptor

• Dalel El-Marrouki,
• Sabrina Touchet,
• Abderrahmen Abdelli,
• Hédi M’Rabet,
• Mohamed Lotfi Efrit and
• Philippe C. Gros

Beilstein J. Org. Chem. 2020, 16, 1722–1731, doi:10.3762/bjoc.16.144

• of the intermediately formed imine to the Michael acceptor (Scheme 3). We then investigated the synthesis of cinnoline derivatives by mixing the diketone 5a and hydrazine monohydrate under various conditions (Table 2). We first investigated the reactivity in ethanol, as a protic solvent, at room

Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review

• Alessandra Del Tito,
• Havall Othman Abdulla,
• Davide Ravelli,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123

• developed, starting from sulfonyl hydrazines in place of sulfonyl chlorides. In this case, the RuII-based photocatalyst was able to reduce tert-butyl peroxybenzoate, triggering the release of a tert-butoxyl radical. This was in turn able to oxidize the hydrazine, allowing the liberation of the desired

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

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

• hydrazine on the more reactive carbon atom of the fluoroenolate in a Michael-type addition. The cyclization did not require a deprotonation of the RNH moiety. Conclusion In summary, a synthesis of fluorinated pyrimidines under mild conditions using fluoroenolate 8 and amidines in a cyclocondensation was

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• to a dichloromethane solution of 2,6-aminopyridine (110) afforded the multidentate ligand 111 in an excellent yield (97%) within 2 h. This in contrast to a method reported by Gaw et al. where the reaction took several days in diethyl ether [104]. Phosphine hydrazine P–N and N–N bonds are labile and

Convenient synthesis of the pentasaccharide repeating unit corresponding to the cell wall O-antigen of Escherichia albertii O4

• Tapasi Manna,
• Arin Gucchait and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2020, 16, 106–110, doi:10.3762/bjoc.16.12

• subjected to a sequence of reactions consisting of (i) reductive transformation of the azido group into an acetamido group by the treatment with thioacetic acid [34]; (ii) transformation of the N-phthalimido group into acetamido group using hydrazine hydrate followed by selective N-acetylation [35]; (iii

Starazo triple switches – synthesis of unsymmetrical 1,3,5-tris(arylazo)benzenes

• Andreas H. Heindl and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2020, 16, 22–31, doi:10.3762/bjoc.16.4

• , 126.2, 123.5, 123.1, 91.5, 56.3, 55.8; HRESIMS (m/z): [M + H]+ calcd for C15H1579Br2N2O3, 428.9444; found, 428.9448. tert-Butyl (E)-2-(3-bromo-5-((2,4,6-trimethoxyphenyl)diazenyl)phenyl)-1-(4-cyanophenyl)hydrazine-1-carboxylate (16a): In a nitrogen-filled glovebox, an oven-dried Schlenk tube was charged

• with a 1.61 M solution of P(t-Bu)3 (395 µL, 636 µmol, 15 mol %) in dry toluene. All following operations were carried out in a fume hood under Schlenk conditions. tert-Butyl 1-(4-cyanophenyl)hydrazine-1-carboxylate (1.00 g, 4.25 mmol, 1.00 equiv), 15 (1.82 g, 4.24 mmol, 1.00 equiv), Pd(OAc)2 (144 mg

• C27H2879BrN5O5Na, 604.1166; found, 604.1167. tert-Butyl (E)-2-(3-bromo-5-((2,4,6-trimethoxyphenyl)diazenyl)phenyl)-1-(4-methoxyphenyl)hydrazine-1-carboxylate (16b): In a nitrogen-filled glovebox, an oven-dried Schlenk tube was charged with P(t-Bu)3 (155 µL, 628 µmol, 15 mol %). All following operations were

Automated glycan assembly of arabinomannan oligosaccharides from Mycobacterium tuberculosis

• Alonso Pardo-Vargas,
• Priya Bharate,
• Martina Delbianco and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2019, 15, 2936–2940, doi:10.3762/bjoc.15.288

• protecting groups, whereby Fmoc was cleaved by piperidine (20 vol % in DMF), while Lev was removed using hydrazine acetate. Iterative cycles continued until the desired structure was obtained. The oligosaccharide products were cleaved from the solid support using a flow UV photoreactor, followed by a two

Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization

• Keishiro Tahara,
• Tetsufumi Nakakita,
• Alyona A. Starikova,
• Takashi Ikeda,
• Masaaki Abe and
• Jun-ichi Kikuchi

Beilstein J. Org. Chem. 2019, 15, 2277–2286, doi:10.3762/bjoc.15.220

• /C (0.0145 g) was refluxed in dry ethanol (10 mL) for 1 h. After dropwise addition of hydrazine monohydrate (0.30 mL), the reaction mixture was refluxed overnight. After filtration of Pd/C and concentrating the filtrate to dryness, the resulting white solid (0.320 g) was identified as 4-amino-4’,4

• mmol) and Pd/C (0.0145 g) in dry ethanol (10 mL) was refluxed for 1 h. After dropwise addition of hydrazine monohydrate (0.30 mL), the reaction mixture was refluxed overnight. After filtration and concentrating the filtrate to dryness, the resulting white solid (0.320 g) was identified as 4-amino-4’,4

Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• state, as envisioned. Possible reasons could be assigned to substituent effects as demonstrated by Simeth et al. [62]. As recently reported by Schehr et al., reducing agents like DTT, used to prevent enzyme oxidation in crystallization mixtures or in vitro assays, can reduce azo dyes to hydrazine

Attempted synthesis of a meta-metalated calix[4]arene

• Christopher D. Jurisch and
• Gareth E. Arnott

Beilstein J. Org. Chem. 2019, 15, 1996–2002, doi:10.3762/bjoc.15.195

• conditions (catalytic palladium on carbon and hydrazine hydrate) was found to be the most efficient method for obtaining monoaminocalix[4]arene 10 in essentially quantitative yields (Scheme 3). The azide-Sandmeyer reaction on monoaminocalix[4]arene 10 was then attempted using sodium nitrite and p

Synthesis and conformational preferences of short analogues of antifreeze glycopeptides (AFGP)

• Małgorzata Urbańczyk,
• Michał Jewgiński,
• Joanna Krzciuk-Gula,
• Jerzy Góra,
• Rafał Latajka and
• Norbert Sewald

Beilstein J. Org. Chem. 2019, 15, 1581–1591, doi:10.3762/bjoc.15.162

• anhydride (50 equiv), DIEA (12.5 equiv), 1-hydroxybenzotriazole (HOBt,1 equiv) in DMF at room temperature for 40 min. Subsequently, the carbohydrate moieties were deacetylated using 1.0 M hydrazine in dry THF at room temperature for 2 hours. The peptides were cleaved from the resin by treatment with 7–10

• -GalNAc)-OH (1 equiv), HOAt (2.25 equiv), HATU (2.8 equiv), DIEA (2.75 equiv), DMF, rt, 3 h; d. Fmoc-L-Ala-OH∙H2O (4 equiv), TBTU (4 equiv), DIEA (4 equiv), DMF, rt, 2 h; e. Ac2O (50 equiv), DIEA (12.5 equiv), HOBt (1 equiv), DMF, rt, 40 min; f. 1.0 M hydrazine in THF, rt, 2 h; g. 7–10% TFA in DCM, rt

Diazocine-functionalized TATA platforms

• Roland Löw,
• Talina Rusch,
• Fynn Röhricht,
• Olaf Magnussen and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1485–1490, doi:10.3762/bjoc.15.150

• of the formed hydrazine (16%). The unprotected ethynyldiazocine 8 was deprotonated with potassium hydroxide and connected to the central carbon atom of the TATA platform 9 (synthesized according to Laursen and Krebs [28]) to obtain target para-diazocine mounted on the octyl-substituted TATA platform

One-pot activation–alkynylation–cyclization synthesis of 1,5-diacyl-5-hydroxypyrazolines in a consecutive three-component fashion

• Christina Görgen,
• Katharina Boden,
• Guido J. Reiss,
• Walter Frank and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 1360–1370, doi:10.3762/bjoc.15.136

• ][51][52], pyrimidines [48][49], and 5-acylpyrazoles [48][49]. The latter 5-acylpyrazole arose after work-up from the three-component AA–cyclocondensation synthesis employing Boc-hydrazine as a binucleophilic hydrazide substrate. Based on our attempts to isolate potential 1,5-diacylpyrazole precursors

• intermediate 5a could be a 1,5-diacylpyrazole. However, upon performing the terminal cyclization step starting from 1,4-diphenylbut-3-yne-1,2-dione (3a) and Boc-hydrazine (4a) under identical conditions 1-Boc-5-benzoyl-5-hydroxypyrazoline was isolated in 83% yield (Scheme 3). The molecular structure was

• . Cyclization of 1,4-diphenylbut-3-yne-1,2-dione (3a) and Boc-hydrazine (4a) to give intermediate 5a. Model reaction for optimizing the activation–alkynylation–cyclization synthesis of 1,5-diacyl-5-hydroxypyrazoline 5b. One-pot activation–alkynylation–cyclization synthesis of 1,5-diacyl-5-hydroxypyrazolines 5