Synthesis of piperidine and pyrrolidine derivatives by electroreductive cyclization of imine with terminal dihaloalkanes in a flow microreactor

• Yuki Naito,
• Naoki Shida and
• Mahito Atobe

Beilstein J. Org. Chem. 2022, 18, 350–359, doi:10.3762/bjoc.18.39

• . Furthermore, piperidine and pyrrolidine derivatives could be obtained on preparative scale by continuous electrolysis for approximately 1 hour. Keywords: electrochemical synthesis; electrocyclization; flow microreactor; heterocyclic amines; imine; Introduction Heterocycles are a very important class of

• compounds and make up more than half of all known organic chemicals [1]. Among them, heterocyclic amines, particularly pyrrolidine and piperidine derivatives, have attracted considerable attention because these are important structural motifs in a wide variety of applications including pharmaceuticals

• ]. Conventional synthetic methods for piperidine derivatives include nucleophilic substitution (route (1) in Scheme 1), reductive amination (route (2)), intramolecular cyclization of amines and alkenes (route (3)), the Diels–Alder reaction and subsequent reduction (route (4)), and the radical cyclization reaction

Unexpected chiral vicinal tetrasubstituted diamines via borylcopper-mediated homocoupling of isatin imines

• Marco Manenti,
• Leonardo Lo Presti,
• Giorgio Molteni and
• Alessandra Silvani

Beilstein J. Org. Chem. 2022, 18, 303–308, doi:10.3762/bjoc.18.34

•  1), evaluating firstly different amines (Table 1, entries 1–5), in place of benzylamine. Using DIPEA, the new product 2a was obtained in 31% yield, even if together with 1-methylisatin and other impurities. Aiming to improve the fruitful conversion of substrate 1a, we considered to reduce the amount

New efficient synthesis of polysubstituted 3,4-dihydroquinazolines and 4H-3,1-benzothiazines through a Passerini/Staudinger/aza-Wittig/addition/nucleophilic substitution sequence

• Long Zhao,
• Mao-Lin Yang,
• Min Liu and
• Ming-Wu Ding

Beilstein J. Org. Chem. 2022, 18, 286–292, doi:10.3762/bjoc.18.32

• isocyanides 3 produced the azide intermediates 4, which were treated sequentially with triphenylphosphine, isocyanates (or CS2), and secondary amines to give polysubstituted 3,4-dihydroquinazolines 8 and 4H-3,1-benzothiazines 11 in good overall yields through consecutive Passerini/Staudinger/aza-Wittig

• of their derivatives [12][13][14][15][16][17][18][19][20][21][22]. For example (Scheme 1), a one-pot Tf2O-mediated assembly of amides, amines, and ketones provided 3,4-dihydroquinazolines in good yields via successive triflic anhydride-mediated amide dehydration, ketimine addition, and Pictet

• product 8a was 53%. Therefore, the reaction conditions of entry 1 in Table 1 were optimal for the above transformation. The optimal reaction conditions were then utilized for the sequential reactions of different 2-azidobenzaldehydes 1, benzoic acid (2a), isocyanides 3, isocyanates and secondary amines

Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions

• Surendran Amrutha,
• Sankaran Radhika and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 262–285, doi:10.3762/bjoc.18.31

• products, pharmaceuticals of biological activity, and materials science [3]. In a Sonogashira reaction, the reaction conditions are mild and many reactions can be performed at room temperature [4]. However, the reaction is usually carried out in organic solvents like amines, benzene, THF, and DMF along

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

New advances in asymmetric organocatalysis

• Radovan Šebesta

Beilstein J. Org. Chem. 2022, 18, 240–242, doi:10.3762/bjoc.18.28

• by a review article devoted to aza-Michael reactions of amines and amides [17]. The evolution of the understanding of noncovalent activation modes led to the realization that anion-binding is a critical feature in many transformations. Halide anions are highly relevant and widely occurring within

Trichloroacetic acid fueled practical amine purifications

• Aleena Thomas,
• Baptiste Gasch,
• Enzo Olivieri and
• Adrien Quintard

Beilstein J. Org. Chem. 2022, 18, 225–231, doi:10.3762/bjoc.18.26

• . Inspired by recent work on out of equilibrium molecular machinery, using trichloroacetic acid (TCA), we disclose a purification technique considerably decreasing the number of operations and the waste generation required for such purifications. At first, TCA triggers the precipitation of the amines through

• their protonated salt formation, enabling the separation with the impurities. From these amine salts, simple decarboxylation of TCA liberates volatile CO2 and chloroform affording directly the pure amines. Through this approach, a broad range of diversely substituted amines could be isolated with

• success. Keywords: amines; decarboxylation; eco-compatible; out of equilibrium; purification; Introduction Isolation of pure amines from reaction mixtures or natural extracts is crucial in modern organic chemistry. However, the most widely applied methods for these purifications have remained unchanged

Organocatalytic asymmetric nitroso aldol reaction of α-substituted malonamates

• Ekta Gupta,
• Narendra Kumar Vaishanv,
• Sandeep Kumar,
• Raja Krishnan Purshottam,
• Ruchir Kant and
• Kishor Mohanan

Beilstein J. Org. Chem. 2022, 18, 217–224, doi:10.3762/bjoc.18.25

• metal-catalyzed reactions [31][32][33][34][35][36]. The most successful among them are the ʟ-proline-catalyzed reactions of enolizable aldehydes with nitrosoarenes [37][38][39][40][41][42][43]. Besides ʟ-proline and its derivatives, various secondary amines derived from BINOL and cinchona alkaloids were

Ready access to 7,8-dihydroindolo[2,3-d][1]benzazepine-6(5H)-one scaffold and analogues via early-stage Fischer ring-closure reaction

• Irina Kuznetcova,
• Felix Bacher,
• Daniel Vegh,
• Hsiang-Yu Chuang and
• Vladimir B. Arion

Beilstein J. Org. Chem. 2022, 18, 143–151, doi:10.3762/bjoc.18.15

• [2,3-d][1]benzazepin-6(5H)-one (3a). This procedure delivered analytically pure 3a in 80% yield as also confirmed by SC-XRD (Figure 3). The final step to structure C required removal of the benzyl group. Debenzylation of amines is commonly performed by palladium-catalyzed hydrogenation [40]. However

Green synthesis of C5–C6-unsubstituted 1,4-DHP scaffolds using an efficient Ni–chitosan nanocatalyst under ultrasonic conditions

• Soumyadip Basu,
• Sauvik Chatterjee,
• Suman Ray,
• Suvendu Maity,
• Prasanta Ghosh,
• Asim Bhaumik and
• Chhanda Mukhopadhyay

Beilstein J. Org. Chem. 2022, 18, 133–142, doi:10.3762/bjoc.18.14

• same time, namely that of an aldehyde and that of one multiple bond. Generally, aldehydes and multiple bonds are very reactive in the presence of primary amines. However, since we used cinnamaldehyde derivatives 3, which are conjugated systems of a double bond and an aldehyde, the reactivity was rather

• The substrate scope and the generality of the reaction under the optimized conditions were explored through the synthesis of various products using differently substituted primary amines 1, cinnamaldehydes 3, and dialkyl but-2-ynedioates 2. Aromatic, aliphatic, benzylic, and various other types of

• primary amines 1 afford an excellent yield. Ortho-, meta-, and para-substituted aromatic amines with both electron-donating and -withdrawing groups were used in this protocol. Aromatic amines with electron-donating groups offered a slightly higher yield compared to those with electron-withdrawing groups

1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

• Ruan Carlos B. Ribeiro,
• Patricia G. Ferreira,
• Amanda de A. Borges,
• Luana da S. M. Forezi,
• Fernando de Carvalho da Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 53–69, doi:10.3762/bjoc.18.5

• , eNovation Chemicals, Tokyo Chemical Industry, Acros Organics, Abcr GmbH, Sigma-Aldrich, and others. Due to this wide commercial availability, these compounds have been widely used in several industrial applications as analytical reagents for the determination of amines and in the synthesis of other hybrid

• -4-sulfonic acid (15) by oxidation with nitric acid in an aqueous medium (Scheme 1A). In 1894, Böniger developed [44] the first reaction of β-NQS with phenylamines. He synthesized β-NQS using a modified method developed by Witt, which quickly reacted with different amines to form colored products

• with amino acids to be used as colorimetric indicators, Folin [45] developed a method based on naphthoquinone since there were records in the literature that indicated that naphthoquinones reacted with amines and proteins to form colored products. Among the tested o-naphthoquinones, he found that 1,2

Recent advances and perspectives in ruthenium-catalyzed cyanation reactions

• Thaipparambil Aneeja,
• Cheriya Mukkolakkal Abdulla Afsina,
• Padinjare Veetil Saranya and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 37–52, doi:10.3762/bjoc.18.4

• 2021. Keywords: cyanation; nitriles; photocatalyst; ruthenium; tertiary amines; Introduction Nitriles are a major class of organic compounds having wide significance in materials science, agrochemical and pharmaceutical industry [1]. They are the privileged compounds finding broad applications in

• natural product synthesis, pigments and dyes. Different variety of α-amino carbonyls [2], α-amino acids [3] and 1,2-diamines were prepared from the nitriles using homogeneous and heterogeneous catalysis [4][5][6]. One of the astonishing aspects of nitriles is that it can be easily converted to amines

• ruthenium complexes which are efficient as catalysts elevated the scope of this metal in synthetic organic chemistry. For clarity and ease of understanding of the topic, this review is categorized into four sections: cyanation of amines, cyanation of arenes and heteroarenes, photocatalyzed cyanation, and

Peptide stapling by late-stage Suzuki–Miyaura cross-coupling

• Hendrik Gruß,
• Rebecca C. Feiner,
• Ridhiwan Mseya,
• David C. Schröder,
• Michał Jewgiński,
• Kristian M. Müller,
• Rafał Latajka,
• Antoine Marion and
• Norbert Sewald

Beilstein J. Org. Chem. 2022, 18, 1–12, doi:10.3762/bjoc.18.1

• only generated with 7-aryl-Trp staple. C) On-resin modification of amines (n = 1: Dab, n = 2: Orn, n = 3: Lys) in i + 4 position to obtain organoboron side chains with increased linker flexibility. Reaction conditions: (a) Pd(PPh3)4, morpholine in DCM, 2 × 20 min; (b) carboxylic acid, HATU, DIEA in DMF

Efficient N-arylation of 4-chloroquinazolines en route to novel 4-anilinoquinazolines as potential anticancer agents

• Rodolfo H. V. Nishimura,
• Thiago dos Santos,
• Valter E. Murie,
• Luciana C. Furtado,
• Leticia V. Costa-Lotufo and
• Giuliano C. Clososki

Beilstein J. Org. Chem. 2021, 17, 2968–2975, doi:10.3762/bjoc.17.206

• antitumor agents, several synthetic methodologies have been developed to prepare these compounds. Amination using primary [6][8][9][10][11][12][13] or secondary [14][15][16] amines and 4-chloroquinazolines is among the most employed procedures. Electron-rich amines (e.g., primary aliphatic amines or hydroxy

• -substituted anilines) [6][9] readily react with 4-chloroquinazolines to give 4-aminoquinazolines in moderate to good yields under milder reaction conditions (Scheme 1a). On the other hand, long reaction times and low yields may be observed when electron-poor amines are applied in these reactions [17][18

DABCO-promoted photocatalytic C–H functionalization of aldehydes

• Bruno Maia da Silva Santos,
• Mariana dos Santos Dupim,
• Cauê Paula de Souza,
• Thiago Messias Cardozo and
• Fernanda Gadini Finelli

Beilstein J. Org. Chem. 2021, 17, 2959–2967, doi:10.3762/bjoc.17.205

• ). Surprisingly, decent amounts of product were observed when the reaction was performed without the use of DABCO (Table 1, entry 9). This result indicates an alternative mechanism can be possible for aryl ketone formation when there are no bicyclic amines in the reaction media. Recent works indicate a bromine

• , Scheme S2). These results highlight the relevance of using bicyclic amines as HAT catalyst for the generality of the scope. Quinuclidine was used instead of DABCO, and similar yields were obtained (Table 1, entry 11), as we expected from a previous publication from the MacMillan group [19]. Once

• amines (Table 1, entries 9 and 10 and Supporting Information File 1, Scheme S2). Radical trapping experiments with TEMPO also showed a radical path mechanism, and the acyl radical was detected as an intermediate (Supporting Information File 1, Table S4). The absence of product formation in the Giese

Study on the interactions between melamine-cored Schiff bases with cucurbit[n]urils of different sizes and its application in detecting silver ions

• Jun-Xian Gou,
• Yang Luo,
• Xi-Nan Yang,
• Wei Zhang,
• Ji-Hong Lu,
• Zhu Tao and
• Xin Xiao

Beilstein J. Org. Chem. 2021, 17, 2950–2958, doi:10.3762/bjoc.17.204

• : cucurbiturils; melamine; Schiff base; silver ion; Introduction Schiff bases [1] are usually synthesized by the condensation of amines and active carbonyl compounds, endowing them both nitrogen and oxygen donor atoms [2][3][4][5]. Schiff bases are not only easy to coordinate with various transition metal ions

A photochemical C=C cleavage process: toward access to backbone N-formyl peptides

• Haopei Wang and
• Zachary T. Ball

Beilstein J. Org. Chem. 2021, 17, 2932–2938, doi:10.3762/bjoc.17.202

• -nitroaryl compounds. Various 2-nitrobenzyl derivatives are used to photocage heteroatom functional groups, including alcohols, amines, carboxylic acids, and phosphates [11]. Typical photochemical pathways result in cleavage of a benzylic C–X bond following initial benzylic H-atom abstraction [11][13]. In

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• rate-determining step of this transformation, as well as free radicals being involved in the reaction mechanism. In 2017, Luo and Li described a three-component Ag-mediated Fe-catalyzed 1,2-carboamination of alkenes 82 using alkyl nitriles 76 and amines 105 for the synthesis of γ-amino alkyl nitriles

• catalyst wasn’t necessary to promote the reaction, but the yield of the cascade was significantly increased upon loading. The scope of the π-systems was limited to alkenes conjugated to electron-rich aryl species. Various nitrogen nucleophiles including primary/secondary amines and sulfonamides were

The PIFA-initiated oxidative cyclization of 2-(3-butenyl)quinazolin-4(3H)-ones – an efficient approach to 1-(hydroxymethyl)-2,3-dihydropyrrolo[1,2-a]quinazolin-5(1H)-ones

• Alla I. Vaskevych,
• Nataliia O. Savinchuk,
• Ruslan I. Vaskevych,
• Eduard B. Rusanov,
• Oleksandr O. Grygorenko and
• Mykhailo V. Vovk

Beilstein J. Org. Chem. 2021, 17, 2787–2794, doi:10.3762/bjoc.17.189

• ring (especially with functional groups) is annulation of the latter moiety to the quinazoline ring. Thus, a series of 1,5-disubstituted pyrroloquinazolines 3 were obtained by a three-component Sonogashira-type coupling of 2-chloro-4-substituted quinazolines 4, propargylic alcohol, and secondary amines

Me₃Al-mediated domino nucleophilic addition/intramolecular cyclisation of 2-(2-oxo-2-phenylethyl)benzonitriles with amines; a convenient approach for the synthesis of substituted 1-aminoisoquinolines

• Krishna M. S. Adusumalli,
• Lakshmi N. S. Konidena,
• Hima B. Gandham,
• Krishnaiah Kumari,
• Krishna R. Valluru,
• Satya K. R. Nidasanametla,
• Venkateswara R. Battula and
• Hari K. Namballa

Beilstein J. Org. Chem. 2021, 17, 2765–2772, doi:10.3762/bjoc.17.186

• achieved by treating 2-(2-oxo-2-phenylethyl)benzonitriles with amines in the presence of Me3Al. The reaction proceeds via a domino nucleophilic addition with subsequent intramolecular cyclisation. This method provides a wide variety of substituted 1-aminoisoquinolines with good functional group tolerance

• the development of several approaches for the efficient construction of these heterocyclic frameworks (Scheme 1). Traditional preparations for 1-aminoisoquinolines include nucleophilic substitution of 1-haloisoquinolines with amines either employing a base [31][32][33][34][35] or a transition metal

• amidines with alkynes catalyzed by either rhodium or ruthenium [55][56][57], or a metal-catalyzed aminative cyclization of 2-alkynylbenzonitriles with secondary amines [58]. Despite the advantages associated with the aforementioned protocols such as the functional group tolerance and huge substrate scope

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• reagent (N-bromophthalimide) plays a crucial role in achieving the excellent selectivities [43]. The axially chiral biaryl-2-amines, N-heteroarenes [44] and derivatives are ubiquitous structural motifs and have profound applications in biochemistry and asymmetric catalysis [45]. These chiral biaryls can

• . The C–H olefination of various biaryl-2-amines with acrylates and styrenes was carried out and afforded the desired products 15 in good yields (up to 96% yield) with high enantioselectivities (up to 96% ee). The electronic properties of the side chains of the biaryl compounds have a significant effect

• on the reactivity, but little on the enantiocontrol. In general, biaryl-2-amines with electron-donating groups showed higher reactivity than those with electron-withdrawing groups (Scheme 6). CPA 5 activates the reaction by creating a rigid and narrow chiral pocket, thus leading to better noncovalent

The ethoxycarbonyl group as both activating and protective group in N-acyl-Pictet–Spengler reactions using methoxystyrenes. A short approach to racemic 1-benzyltetrahydroisoquinoline alkaloids

• Marco Keller,
• Karl Sauvageot-Witzku,
• Franz Geisslinger,
• Nicole Urban,
• Michael Schaefer,
• Karin Bartel and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2716–2725, doi:10.3762/bjoc.17.183

• reduction of the intermediate nitrostyrenes and N-ethoxycarbonylation of the resulting primary amines [15]. For the synthesis of the alkaloids rac-reticuline (2e) and rac-orientaline (2f) we used a carbamate building block A3 without protection of the phenolic group, since our previous work [10

Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone

• Ilya A. P. Jourjine,
• Lukas Zeisel,
• Jürgen Krauß and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2668–2679, doi:10.3762/bjoc.17.181

• secondary and tertiary amines, amides/lactams/carbamates, and nitrile. The test reactions were monitored by thin-layer chromatography (TLC) and, where deemed necessary, results were further verified by GC–MS. The reagents employed encompassed tritylium tetrafluoroborate [50], H2O2/HBr [42], ceric ammonium

• /reagent combinations employed. The reaction of the secondary N-methylamine 2b with CBr4 [22] gave fluorenone (3) in 6% yield (determined by GC–MS), while tertiary amines, amides, and the γ-lactam 2e did not yield any. Formation of fluorenone (3) was also confirmed after applying a modified version of one

• amines 2c, 2d, and 2f, albeit in drastically lower yield (Table 1, entries 3, 4, and 6). Initially, our focus was on testing tertiary amines, as we speculated that the electrophilic iminium species 4a (R1, R2 = alkyl; Scheme 3) would form more easily with stabilizing electron-donating alkyl substituents

N-Sulfinylpyrrolidine-containing ureas and thioureas as bifunctional organocatalysts

• Viera Poláčková,
• Dominika Krištofíková,
• Boglárka Némethová,
• Renata Górová,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2021, 17, 2629–2641, doi:10.3762/bjoc.17.176

• itself, in which the carboxylic function acts as an ancillary hydrogen-bond donor for the direction of one of the reagents [9]. Amines serve as basic units and nucleophilic components capable of carbonyl compounds activation via enamine or iminium ion formation [10][11]. In particular, pyrrolidine became

Recent advances in organocatalytic asymmetric aza-Michael reactions of amines and amides

• Pratibha Sharma,
• Raakhi Gupta and
• Raj K. Bansal

Beilstein J. Org. Chem. 2021, 17, 2585–2610, doi:10.3762/bjoc.17.173

• overviews the literature published during the last 10 years concerning the asymmetric aza-MR of amines and amides catalysed by organocatalysts. Both types of the organocatalysts, i.e., those acting through non-covalent interactions and those working through covalent bond formation have been applied for the

• asymmetric aza-MR. Thus, the review includes the examples wherein cinchona alkaloids, squaramides, chiral amines, phase-transfer catalysts and chiral bifunctional thioureas have been used, which activate the substrates through hydrogen bond formation. Most of these reactions are accompanied by high yields

• aromatic amines, amides, imides, etc. require the use of an appropriate catalyst to undergo a Michael addition with a suitable acceptor. In view of this, chemists endeavoured to develop different types of catalysts, particularly the chiral catalysts to accomplish asymmetric aza-MRs. The development of