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

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• treat schizophrenia. In an interesting report Aggarwal et al. [74] described the synthesis of 4,7-dihydropyrazolo[3,4-b]pyridine-5-nitriles 92 from the reaction of β-ketonitriles 15 with several aryl/heteroaryl hydrazines 14 in ethanol with a catalytic amount of conc. HNO3 (Scheme 26). The authors

Progress in copper-catalyzed trifluoromethylation

• Guan-bao Li,
• Chao Zhang,
• Chun Song and
• Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

• )–H with a electrophilic trifluoromethylation reagent (Togni’s reagent): N,N-Dialkylhydrazones were widely used in organic chemistry, including using as synthetic equivalents of carbonyl compounds, as precursors to substituted hydrazines or primary amines. In 2013, Baudoin and co-workers [53] firstly

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• disulfide, thioamide derivatives and sulfides Disulfides and thiosulfates Sulfoxides Sulfinic acids, sulfinate salts and sulfinamides Sulfonyl halides, sulfonyl hydrazines, thionyl chloride and sulfur dioxide C–S bond formations initiated by irradiation with light of wavelengths shorter than 380 nm or by

Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269

• nucleophile then attacks the β-position of the vinylphosphonium salt 64, resulting in the expected resonance-stabilized ylide 65 [62]. The corresponding ylides 66 were also obtained in high yields of 90–94% in an analogous reaction by the use of aryl hydrazines (Scheme 43) [62]. The same type of reaction but

• phosphorus ylides via the reaction of triphenylphosphine with dialkyl acetylenedicarboxylates and arylsulfonic hydrazides. Synthesis of resonance-stabilized phosphorus ylides in the reaction of triphenylphosphine, dialkyl acetylenedicarboxylates, and aryl hydrazines. Synthesis of resonance-stabilized

A concise flow synthesis of indole-3-carboxylic ester and its derivatisation to an auxin mimic

• Marcus Baumann,
• Ian R. Baxendale and
• Fabien Deplante

Beilstein J. Org. Chem. 2017, 13, 2549–2560, doi:10.3762/bjoc.13.251

• new entries into these valuable structures [6]. However, common to the majority of these indole syntheses is the use of hazardous entities such as hydrazines (Fischer), diazonium species (Japp–Klingemann) or azides (Hemetsberger–Knittel) or the necessity to construct specifically functionalised

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• dicyanofumarates E-1 with 1-azabicyclo[1.1.0]butanes 55. Formation of pyrazole derivatives in the reaction of hydrazines with E-1. Formation of 5-aminopyrazole-3,4-dicarboxylate 65 via heterocyclization reactions. Reactions of aryl- and hetarylcarbohydrazides 67 with E-1a. Multistep reaction leading to

Transition-metal-free synthesis of 3-sulfenylated chromones via KIO₃-catalyzed radical C(sp²)–H sulfenylation

• Yanhui Guo,
• Shanshan Zhong,
• Li Wei and
• Jie-Ping Wan

Beilstein J. Org. Chem. 2017, 13, 2017–2022, doi:10.3762/bjoc.13.199

• Yanhui Guo Shanshan Zhong Li Wei Jie-Ping Wan College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022, P.R. China 10.3762/bjoc.13.199 Abstract The reactions between o-hydroxylphenyl-functionalized enaminones and sulfonyl hydrazines providing 3-sulfenylated

• protocol toward these compounds through the tandem reactions between o-hydroxyphenylenaminones and sulfonyl hydrazines. In this method, the construction of the target products is furnished via the key C–H sulfenylation without using any transition metal catalyst or oxidative additive. Results and

• ), prolonging the reaction time to 24 h was found to be capable of further improving the yield of 3a (entries 16 and 17, Table 1). To examine the scope of the reaction, enaminones 1 containing different functional groups as well as various sulfonyl hydrazines 2 were subjected to the optimized standard reaction

Synthesis of tetrasubstituted pyrazoles containing pyridinyl substituents

• Josef Jansa,
• Ramona Schmidt,
• Ashenafi Damtew Mamuye,
• Laura Castoldi,
• Alexander Roller,
• Vittorio Pace and
• Wolfgang Holzer

Beilstein J. Org. Chem. 2017, 13, 895–902, doi:10.3762/bjoc.13.90

• most common strategies employ reactions of 1,3-dicarbonyl compounds or α,β-unsaturated carbonyl compounds with substituted hydrazines [4][6][19]. To overcome the drawbacks of this method, namely insufficient regioselectivity [20], other accesses such as, for instance, regioselective metalations of N

Synthesis and optical properties of new 5'-aryl-substituted 2,5-bis(3-decyl-2,2'-bithiophen-5-yl)-1,3,4-oxadiazoles

• Anastasia S. Kostyuchenko,
• Tatyana Yu. Zheleznova,
• Anton J. Stasyuk,
• Aleksandra Kurowska,
• Wojciech Domagala,
• Adam Pron and
• Alexander S. Fisyuk

Beilstein J. Org. Chem. 2017, 13, 313–322, doi:10.3762/bjoc.13.34

• alcohol. The diacyl hydrazines 14b,c were obtained through the coupling of the hydrazide derivatives 13b,c with carboxylic acids 12b,c in the presence of N,N'-dicyclohexylcarbodiimide (DCC) as reported earlier [18]. A modified procedure, which avoids the preparation of hydrazides 13, was used for the

• the obtained diacylated hydrazines 14b–g were in the range of 58–74% (Scheme 3). Finally, heating the diacyl hydrazines 14b–g in phosphorus oxychloride led to the formation of the desired 1,3,4-oxadiazoles 15b–g. The product yields were between 65–94% after purification by column chromatography

• -carboxylic acids 7d–g. Synthesis of diacyl hydrazines 14b–g. Synthesis of 5'-aryl-substituted 2,5-bis(3-decyl-2,2'-bithiophen-5-yl)-1,3,4-oxadiazoles 15b–g. Reaction conditions and yields for the synthesis of ethyl 5'-aryl-3-decyl-2,2'-bithiophene-5-carboxylates 7d–g. Spectroscopic and luminescent properties

Extrusion – back to the future: Using an established technique to reform automated chemical synthesis

• Deborah E. Crawford

Beilstein J. Org. Chem. 2017, 13, 65–75, doi:10.3762/bjoc.13.9

• materials can be used in the extruder, through the use of s-Buli by Höcker et al., reagents that are potentially explosive or can be ignited when dry or exposed to friction are too hazardous to be used in an extrusion process, therefore chemistry involving azides or hydrazines for example, would need to be

2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties

• Yury A. Sayapin,
• Inna O. Tupaeva,
• Alexandra A. Kolodina,
• Eugeny A. Gusakov,
• Vitaly N. Komissarov,
• Igor V. Dorogan,
• Nadezhda I. Makarova,
• Anatoly V. Metelitsa,
• Valery V. Tkachev,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2015, 11, 2179–2188, doi:10.3762/bjoc.11.236

• of 2-acyl-5,6,7-trichloro-1,3-tropolones under the action of alcohols [17][32] or hydrazines [32] has been previously reported. The suggested primary step of these reactions is a nucleophilic addition to the carbonyl carbon of an acyl group. In our case (compounds 5 and 6), the reaction most probably

A convenient four-component one-pot strategy toward the synthesis of pyrazolo[3,4-d]pyrimidines

• Mingxing Liu,
• Jiarong Li,
• Hongxin Chai,
• Kai Zhang,
• Deli Yang,
• Qi Zhang and
• Daxin Shi

Beilstein J. Org. Chem. 2015, 11, 2125–2131, doi:10.3762/bjoc.11.229

• -component condensation of hydrazines, methylenemalononitriles, aldehydes and alcohols has been developed via two different reaction pathways. The structures of target products were characterized by IR spectroscopy, NMR (1H and 13C) spectroscopy and HRMS (ESI) spectrometry. The crystal structure of 4-ethoxy

• , this is a novel methodology for the synthesis of pyrazolo[3,4-d]pyrimidines by the reaction of hydrazines, methylenemalononitriles, aldehydes and alcohols. During the preparation of this manuscript, Liu et al. reported the synthesis of pyrazolo[3,4-d]pyrimidines from 5-aminopyrazole-4-carbonitrile [48

• a catalyst, but also participates in the reaction. A series of hydrazines, methylenemalononitriles, aldehydes and alcohols were investigated under the optimal reaction conditions. As shown in Figure 1, the influence of different aldehydes on the reaction was studied first. The results show that

Three-component synthesis of C₂F₅-substituted pyrazoles from C₂F₅CH₂NH₂·HCl, NaNO₂ and electron-deficient alkynes

• Pavel K. Mykhailiuk

Beilstein J. Org. Chem. 2015, 11, 16–24, doi:10.3762/bjoc.11.3

• -dicarbonyl compounds (or their synthons) with hydrazines [39][40][41][42][43][44]. In this context, novel practical methods to C2F5-pyrazoles are needed. Last year, Ma and colleagues synthesized CF3-pyrazoles by [3 + 2] cycloaddition between in situ generated CF3CHN2 and alkynes [45]. This method, however

Synthesis of a bifunctional cytidine derivative and its conjugation to RNA for in vitro selection of a cytidine deaminase ribozyme

• Nico Rublack and
• Sabine Müller

Beilstein J. Org. Chem. 2014, 10, 1906–1913, doi:10.3762/bjoc.10.198

• properties of the RNA's 3'-terminal cis-diol, which can be specifically oxidized with metaperiodate [26][27][28], followed by reaction of the produced dialdehyde with amines or hydrazines linked to a desired functional entity [29]. We set out to select from a random library catalytically active RNAs that

Regioselective S_N2' Mitsunobu reaction of Morita–Baylis–Hillman alcohols: A facile and stereoselective synthesis of α-alkylidene-β-hydrazino acid derivatives

• Silong Xu,
• Jian Shang,
• Junjie Zhang and
• Yuhai Tang

Beilstein J. Org. Chem. 2014, 10, 990–995, doi:10.3762/bjoc.10.98

• triphenylphosphine is developed, which provides an easy access to α-alkylidene-β-hydrazino acid derivatives in high yields and good stereoselectivity. This reaction represents the first direct transformation of MBH alcohols into hydrazines. Keywords: azodicarboxylate; hydrazine; Mitsunobu reaction; Morita–Baylis

• –Hillman; SN2' reaction; Introduction Hydrazines and their derivatives are an important class of compounds in organic chemistry. They are widely used in the fields of pesticides, polymers, dyestuff, and pharmaceutical agents [1]. They are also versatile building blocks for accessing many important

• nitrogen-containing heterocyclic compounds, especially pyrazole derivatives [2][3][4][5][6][7]. Although various methods detailing the synthesis of hydrazines have been established [8], the development of an efficient synthesis of hydrazines with highly structural diversity from simple starting materials

Use of activated enol ethers in the synthesis of pyrazoles: reactions with hydrazine and a study of pyrazole tautomerism

• Denisa Tarabová,
• Stanislava Šoralová,
• Martin Breza,
• Marek Fronc,
• Wolfgang Holzer and
• Viktor Milata

Beilstein J. Org. Chem. 2014, 10, 752–760, doi:10.3762/bjoc.10.70

• trifunctional electrophiles and are useful building blocks for the introduction of a three carbon fragment into the resulting molecule. Thus, the reaction of enol ethers with hydrazines produces pyrazoles, with amidines pyrimidines, with hydroxylamine isoxazoles, and with anilines quinolines/ones are formed [2

• and are mostly prepared by reacting hydrazines with suitable 1,3-dielectrophiles. The synthesis of pyrazoles and related compounds can be implemented by four different approaches: reaction of (substituted) hydrazines with β-functional compounds or their equivalents (the most frequently used method

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

• functionalized dihydropyrazoles 13 starting from aryl/alkylacetylenes, aldehydes – and also more challenging ketones – and N-Boc-N’-substituted hydrazines 14 [41] (Scheme 12). Among several gold complexes tested, best results were obtained with IPrAuCl/AgOTf (2–5 mol %) in DCE (AcOH for aromatic aldehydes) at 50

IBD-mediated oxidative cyclization of pyrimidinylhydrazones and concurrent Dimroth rearrangement: Synthesis of [1,2,4]triazolo[1,5-c]pyrimidine derivatives

• Caifei Tang,
• Zhiming Li and
• Quanrui Wang

Beilstein J. Org. Chem. 2013, 9, 2629–2634, doi:10.3762/bjoc.9.298

• investigation commenced with the preparation of 1-(6-chloropyrimidin-4-yl)hydrazines 3. The required starting 4,6-dihydroxypyrimidines 1 can be prepared following the reported procedure by condensation of dimethyl malonate either with formamide (for 1a) or the respective formamidine salts (for 1b and 1c) [15

• -yl)hydrazines 3 were then obtained in 90–95% yield through the reaction of compounds 2 with two equivalents of 50% hydrazine in ethanol at 45 °C for 2 h (Scheme 1). We next examined the synthesis of the corresponding hydrazones of various aldehydes. After screening a set of conditions, optimal

• reactions, which are under investigation in our group. The structure of two representatives of [1,2,4]triazolopyrimidines. Synthesis of 1-(6-chloropyrimidin-4-yl)hydrazines 3. Plausible mechanism for the transformation of [1,2,4]triazolo[4,3-c]pyrimidines 5 to the [1,5-c] series 6. Synthesis of the

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• ion furnishes a new amine radical cation 152. Finally, amine radical cation 152 is reduced by Ru(I) to provide the annulation product 153 and regenerate Ru(II), thus completing the catalytic cycle. Our group also realized cleavage of N–N bonds by irradiation of aromatic hydrazines or hydrazides in the

• presence of Ru(bpz)3(PF6)2 and air (Scheme 34) [108]. A 13 W compact fluorescent light was sufficient as the light source. N,N-disubstituted hydrazines and hydrazides were suitable substrates provided that at least one of the two substituents on the nitrogen atom was an aryl group. Electron-richer

• hydrazines were found to be more reactive than hydrazides. This is consistent with our expectation that, similar to amines, hydrazines and hydrazides act as an electron donor to reductively quench the photoexcited Ru(II) complex. The photoexcited state of Ru(bpz)3 (E1/2*II/I = 1.45 V vs SCE) is more

One-step synthesis of pyridines and dihydropyridines in a continuous flow microwave reactor

• Mark C. Bagley,
• Vincenzo Fusillo,
• Robert L. Jenkins,
• M. Caterina Lubinu and
• Christopher Mason

Beilstein J. Org. Chem. 2013, 9, 1957–1968, doi:10.3762/bjoc.9.232

• . [47] have demonstrated that ethynyl ketones can be generated in flow by the palladium-catalysed acylation of terminal alkynes and further transformed in a continuous process to pyrazoles by cyclocondensation with hydrazines using a commercially available conductive heating modular flow reactor. Given

Organocatalytic cascade aza-Michael/hemiacetal reaction between disubstituted hydrazines and α,β-unsaturated aldehydes: Highly diastereo- and enantioselective synthesis of pyrazolidine derivatives

• Zhi-Cong Geng,
• Jian Chen,
• Ning Li,
• Xiao-Fei Huang,
• Yong Zhang,
• Ya-Wen Zhang and
• Xing-Wang Wang

Beilstein J. Org. Chem. 2012, 8, 1710–1720, doi:10.3762/bjoc.8.195

• -pyrazolines starting from α,β-unsaturated ketones and phenylhydrazine or N-tert-butyloxycarbonylhydrazine in the presence of a chiral Brønsted acid or a phase-transfer catalyst [70][71]. Compared with monosubstituted hydrazines in organocatalytic asymmetric synthesis, disubstituted hydrazines were also

• of 2-pyrazolines using disubstituted hydrazines through an asymmetric conjugate addition followed by a deprotection–cyclization sequence [75]. Due to the importance of pyrazolidine derivatives in both organic and medicinal chemistry, we have become interested in developing an efficient

• stereoselective cascade reaction for the synthesis of the pyrazolidine compounds through organocatalysis. In this paper, we present a convenient access to racemic and enantioenriched 5-hydroxypyrazolidines through a domino aza-Michael/hemiacetal organocatalytic sequence of disubstituted hydrazines to α,β

Chemo-enzymatic modification of poly-N-acetyllactosamine (LacNAc) oligomers and N,N-diacetyllactosamine (LacDiNAc) based on galactose oxidase treatment

• Christiane E. Kupper,
• Ruben R. Rosencrantz,
• Birgit Henßen,
• Helena Pelantová,
• Stephan Thönes,
• Anna Drozdová,
• Vladimir Křen and
• Lothar Elling

Beilstein J. Org. Chem. 2012, 8, 712–725, doi:10.3762/bjoc.8.80

• reduced with Na[BH3(CN)] to the corresponding hydrazines (15a–c and 16a). B: Elongation of biotinylated LacNAc (15a) and biotinylated tetrasaccharide (15b) by β3-N-acetylglucosaminyltransferase (β3GlcNAc-transferase) leads to an internally modified trisaccharide 16a as the enzymatic elongation of the

Synthesis of oleophilic electron-rich phenylhydrazines

• Aleksandra Jankowiak and
• Piotr Kaszyński

Beilstein J. Org. Chem. 2012, 8, 275–282, doi:10.3762/bjoc.8.29

• increases its stability in the reaction medium. The hydrazines were isolated in 60–86% yields and purities >90%. The hydrazides 2 were obtained in 43–71% yields from aryl bromides 5, which were lithiated with t-BuLi and subsequently reacted with di-tert-butyl azodicarboxylate (DTBAD). Keywords

• deprotection of Boc-substituted hydrazines (Scheme 2), hydrazides 2, expecting that the reaction could be performed under fully homogenous conditions. Analysis of the reaction mechanism for the deprotection of 2 under acidic conditions shows that removal of the Boc group generates t-Bu+, which reacts with the

• be optimum; the purity of the hydrazine decreased with increasing reaction times. By using this protocol, hydrazines 1 were isolated as viscous oils in purities >90% and yields of 60–86%, according to 1H NMR analysis with 1,4-dimethoxybenzene as the internal standard (Scheme 3). Attempts at the

Derivatives of phenyl tribromomethyl sulfone as novel compounds with potential pesticidal activity

• Krzysztof M. Borys,
• Maciej D. Korzyński and
• Zbigniew Ochal

Beilstein J. Org. Chem. 2012, 8, 259–265, doi:10.3762/bjoc.8.27

• ammonia, amines, hydrazines and phenolates to give 2-nitroaniline, 2-nitrophenylhydrazine and diphenyl ether derivatives. Reduction of the nitro group of 4-tribromomethylsulfonyl-2-nitroaniline yielded the corresponding o-phenylenediamine substrate for preparation of structurally varied benzimidazoles