HPW-Catalyzed environmentally benign approach to imidazo[1,2-a]pyridines

• Luan A. Martinho and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2024, 20, 628–637, doi:10.3762/bjoc.20.55

• activities. The most direct way of obtaining this nucleus is the Groebke–Blackburn–Bienaymé three-component reaction (GBB-3CR) between aminopyridines, aldehydes, and isocyanides under both Lewis and Brønsted acid catalysis. However, several catalysts for this reaction have major drawbacks such as being

• conditions and the employment of relatively complex starting materials [19]. A more efficient way of obtaining this nucleus is through the Groebke–Blackburn–Bienaymé three-component reaction (GBB-3CR) between amidines (aminoazoles), aldehydes, and isocyanides under both Lewis and Brønsted acid catalysis [20

• 1, aromatic/heteroaromatic aldehydes 2, and isocyanides 3 to obtain the imidazo[1,2-a]pyridine derivatives 4 (Scheme 2). In general, the efficiency of the HPW-catalyzed GBB reaction is very dependent upon the type of 2-aminopyridine or isocyanide compound used, and not influenced by different

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

• HCl-promoted 1,2-thiofunctionalization of aromatic alkenes. Coupling reaction of diazo compounds with N-sulfenylsuccinimides. Multicomponent reactions of disulfides with isocyanides and other nucleophiles. α-Sulfenylation and β-sulfenylation of α,β-unsaturated carbonyl compounds.

Synthesis of imidazo[1,2-a]pyridine-containing peptidomimetics by tandem of Groebke–Blackburn–Bienaymé and Ugi reactions

• Oleksandr V. Kolomiiets,
• Alexander V. Tsygankov,
• Maryna N. Kornet,
• Aleksander A. Brazhko,
• Vladimir I. Musatov and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2023, 19, 727–735, doi:10.3762/bjoc.19.53

• peptidomimetic chain was already described in 2010 [32]. Thus, the corresponding acid components were synthesized with GBB-3CR and used in Ugi and Paserini reactions with various aldehydes, amines (for Ugi) and isocyanides. Moreover, in 2016 [33], an alternative route to use GBB-3CR products in Ugi reaction as

• temperature and the reaction time. After a series of experiments, it was found that stirring the isocyanides 3a–d, heterocyclic acids 4a–c, aldehydes 5a–e, and primary amines 6a–d at 50 °C in methanol for 24–48 hours (depending on the nature of the starting materials) allowed obtaining the Ugi target products

Nucleophile-induced ring contraction in pyrrolo[2,1-c][1,4]benzothiazines: access to pyrrolo[2,1-b][1,3]benzothiazoles

• Ekaterina A. Lystsova,
• Maksim V. Dmitriev,
• Andrey N. Maslivets and
• Ekaterina E. Khramtsova

Beilstein J. Org. Chem. 2023, 19, 646–657, doi:10.3762/bjoc.19.46

• -benzothiazol-2-yl(diazo)acetates (Scheme 1, entry 3) [12], dearomative [3 + 2] cycloaddition reactions of benzothiazoles with cyclopropanes (Scheme 1, entry 4) [13][14][15], multicomponent reactions (MCRs) of benzothiazoles, isocyanides and 2-methylidenemalonates (Scheme 1, entry 5) [16], 1,3-dipolar

Group 13 exchange and transborylation in catalysis

• Dominic R. Willcox and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2023, 19, 325–348, doi:10.3762/bjoc.19.28

• hydroboration of imines [87][92][97], nitriles [92][98][99][100][101], carbodiimides [92][100][102], pyridine [92], and isocyanides [92] with HBpin (Scheme 23). These generally follow a similar proposed catalytic cycle; aluminium-mediated reduction, followed by Al‒N/B‒H exchange with HBpin (Scheme 23). The

NaI/PPh₃-catalyzed visible-light-mediated decarboxylative radical cascade cyclization of N-arylacrylamides for the efficient synthesis of quaternary oxindoles

• Dan Liu,
• Yue Zhao and
• Frederic W. Patureau

Beilstein J. Org. Chem. 2023, 19, 57–65, doi:10.3762/bjoc.19.5

• /cyclization cascades from acrylamides for the synthesis of oxindoles [39][40][41]. The radicals are typically generated from alkyl halides [42][43][44], carboxylic acids [45][46][47], simple alkanes [48], alkylboronic acids [49], isocyanides [50], or other [51][52][53]. In this context, the group of Fu

Dissecting Mechanochemistry III

• Lars Borchardt and
• José G. Hernández

Beilstein J. Org. Chem. 2022, 18, 1454–1456, doi:10.3762/bjoc.18.150

• the use of halogenated compounds and include the mechanochemical preparation of isocyanides [10], formylated and acetylated amines [11], and the mechanosynthesis of unsymmetrical salens ligands for preparing metal–salen catalysts [12]. This illustrates the broad applicability of mechanochemical

From amines to (form)amides: a simple and successful mechanochemical approach

• Federico Casti,
• Rita Mocci and
• Andrea Porcheddu

Beilstein J. Org. Chem. 2022, 18, 1210–1216, doi:10.3762/bjoc.18.126

• products [1][9]. N-Formyl derivatives were used as building blocks in Vilsmeier–Haack reactions [10][11] and for preparing molecule drug substances, various heterocycles, formamidines, isocyanates, and isocyanides [12][13][14][15][16][17]. The large number of procedures reported in the literature witnesses

• reactions [35][36][37][38][39][40][41][42]. In our effort to develop green and sustainable methodologies using mechanochemistry [43][44][45][46], we recently studied a protocol for synthesizing isocyanides using p-tosyl chloride (Ts-Cl) in basic conditions, starting from the corresponding formamides [47

• compatible means in the view of a one-pot methodology for preparing isocyanides directly from amines [56]. When the amine 1 was reacted in the presence of Et3N, HCOOH, and p-Ts-Im [58] (Table 1, entry 5), the formamide was accompanied by a significant amount of sulfonamide (formamide/sulfonamide ratio: 70:30

A trustworthy mechanochemical route to isocyanides

• Francesco Basoccu,
• Federico Cuccu,
• Federico Casti,
• Rita Mocci,
• Claudia Fattuoni and
• Andrea Porcheddu

Beilstein J. Org. Chem. 2022, 18, 732–737, doi:10.3762/bjoc.18.73

• Francesco Basoccu Federico Cuccu Federico Casti Rita Mocci Claudia Fattuoni Andrea Porcheddu Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, Cittadella Universitaria, Monserrato, 09042 Cagliari, Italy 10.3762/bjoc.18.73 Abstract Isocyanides are hardly produced

• straightforward procedure. Keywords: green chemistry; isocyanide; isonitriles; mechanochemistry; Introduction Isocyanides were first discovered more than a century ago by Lieke in Göttingen after having handled allyl iodide and potassium cyanide to synthesize crotonic acid. This attempt, instead, brought to the

• envisioned the feasibility of producing isocyanides from primary formamides by using anhydrides as dehydrating agents. Therefore, we focused our attention on acetic, trifluoroacetic, and isatoic anhydrides to achieve this. First attempts were made on acetic and trifluoroacetic anhydrides. The best results

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

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

• 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 advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

• Yi Liu,
• Puying Luo,
• Yang Fu,
• Tianxin Hao,
• Xuan Liu,
• Qiuping Ding and
• Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

• products 52 were obtained efficiently through the cascade reactions of enynals 51, primary amines, aliphatic isocyanides, and trimethylsilyl azide. The following reaction involves Ag-catalyzed intramolecular 5-endo-dig cyclization and base (DMAP)-promoted oxidative isomerization. The presence of DMAP is

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• through an isocyanide insertion. The significant benefits of this strategy were simple substrates, few synthetic steps, and high diversity. A range of o‐azidophenols 148 as well as the compounds 150 and 151, along with alkynes 149 and isocyanides, were employed to survey the diversity of highly

• functionalized tricyclic triazoles 152–154. It was proved that o‐azidophenols 148 react well with alkynes 149 using CuI in DMF at 120 °C and then, the resulting intermediates react with isocyanides using Pd(OAc)2 and an O2 atmosphere at 120 °C to produce the desired products (Scheme 42). o‐Azidophenols 148 were

One-step synthesis of imidazoles from Asmic (anisylsulfanylmethyl isocyanide)

• Louis G. Mueller,
• Allen Chao,
• Embarek AlWedi and
• Fraser F. Fleming

Beilstein J. Org. Chem. 2021, 17, 1499–1502, doi:10.3762/bjoc.17.106

• a valuable route to mono- and disubstituted imidazoles. Keywords: Asmic; cyclization; imidazoles; isocyanides; nitriles; Introduction The imidazole core is the seventh most prevalent heterocycle among nitrogen-containing pharmaceuticals [1]. The privileged efficacy of imidazoles emanates from the

• to imidazoles [11][12], the condensation of metalated isocyanides with nitrogenous π-electrophiles is distinguished by excellent efficiency and modularity. Deprotonating an isocyanide 1 affords an isocyanide-stabilized anion 2 whose condensation with an imidate or nitrile generates a transient imine

• 3 that readily cyclizes to afford imidazole 4 (Scheme 1). The excellent efficiency is somewhat countered by requiring isocyanides that are readily deprotonated; metalation of alkylisocyanides is challenging except for methyl isocyanide which is why most isocyanides employed in accessing imidazoles

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

• ] tailored a microwave-assisted multicomponent reaction for fast and efficient generation of diastereoselective dibenzo[c,e]azepinones. The protocol utilized substituted 2'-formylbiphenyl-2-carboxylic acid 19, benzylamines 20, and isocyanides 21 in TFE and Na2SO4 as drying agent for the construction of

• . One such demonstration was reported by Padmini and co-workers [64] wherein a four-component reaction between substituted aldehydes 5, phenanthroline (63), malononitrile (51) and isocyanides 21 afforded pyrrolo[1,10]-phenanthrolines 64 in ethanol as a solvent with excellent yields. The conventional

• -phenanthrolines and affords intermediate C. A subsequent cyclization D and aromatization E with loss of HCN yield the desired products 64. The lower yields in case of aliphatic isocyanides were reasoned with its low nucleophilicity losing the competition with aryledenemalononitrile A in the reaction with

Effective microwave-assisted approach to 1,2,3-triazolobenzodiazepinones via tandem Ugi reaction/catalyst-free intramolecular azide–alkyne cycloaddition

• Maryna O. Mazur,
• Oleksii S. Zhelavskyi,
• Eugene M. Zviagin,
• Svitlana V. Shishkina,
• Vladimir I. Musatov,
• Maksim A. Kolosov,
• Elena H. Shvets,
• Anna Yu. Andryushchenko and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2021, 17, 678–687, doi:10.3762/bjoc.17.57

• Chemistry, University of Nebraska – Lincoln, 639 N 12th St, Lincoln, NE 68588, USA 10.3762/bjoc.17.57 Abstract A novel catalyst-free synthetic approach to 1,2,3-triazolobenzodiazepinones has been developed and optimized. The Ugi reaction of 2-azidobenzaldehyde, various amines, isocyanides, and acids

• more efficient but also more toxic HMPA. A few modifications made in the original procedure in combination with column chromatography led to pure product 2 in good yield (Scheme 2). With azide precursor 2 in hand as an aldehyde component, the Ugi reaction was performed with various isocyanides 4

Amino- and polyaminophthalazin-1(2H)-ones: synthesis, coordination properties, and biological activity

• Zbigniew Malinowski,
• Emilia Fornal,
• Agata Sumara,
• Renata Kontek,
• Karol Bukowski,
• Beata Pasternak,
• Dariusz Sroczyński,
• Joachim Kusz,
• Magdalena Małecka and
• Monika Nowak

Beilstein J. Org. Chem. 2021, 17, 558–568, doi:10.3762/bjoc.17.50

• -bromobenzoate via palladium-catalyzed isocyanide insertion [32][33] (a method that is limited to tertiary-substituted isocyanides) or 2) the palladium or copper-catalyzed coupling of bromolactams with amines (a method that requires the usually lengthy synthesis of the bromoprecursors) [19][34]. Therefore, the

Controlling the stereochemistry in 2-oxo-aldehyde-derived Ugi adducts through the cinchona alkaloid-promoted electrophilic fluorination

• Yuqing Wang,
• Gaigai Wang,
• Anatoly A. Peshkov,
• Ruwei Yao,
• Muhammad Hasan,
• Manzoor Zaman,
• Chao Liu,
• Stepan Kashtanov,
• Olga P. Pereshivko and
• Vsevolod A. Peshkov

Beilstein J. Org. Chem. 2020, 16, 1963–1973, doi:10.3762/bjoc.16.163

• -component Passerini [19][20][21][22] and four-component Ugi [23][24] reactions that rely on the ability of organic isocyanides to participate in the nucleophilic attack onto the carbonyl or imine group are among the most studied MCRs. Accordingly, a wide range of post-MCR transformations have been

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

• biaryls 5.1a–d in up to excellent yields at room temperature by using α-bromoesters as radical precursors and [fac-Ir(ppy)3] as the photoredox catalyst [49]. A similar photocatalyzed tandem insertion/cyclization approach based on isocyanides and amino acid/peptide-derived Katritzky salts as precursors of

• - [55][56] phenanthridines was investigated. On the other hand, Umemoto’s reagent 7.2 was widely employed to introduce a trifluoromethyl group. In one instance, the visible-light irradiation of isocyanides 7.1 in the presence of excess 7.2 (4 equiv) and the Ru(bpy)32+ photoredox catalyst afforded the

• lamp (280–780 nm), in a photocatalyst-free fashion [61]. Easily scalable and thermally stable arylthiodifluoromethyl 2-pyridyl sulfones were likewise exploited in the visible-light photocatalyzed arylthiodifluoromethylation of differently substituted isocyanides [62]. 6-Arylphenanthridines were

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• involving an isonitrile group is the reaction of β,γ-unsaturated oximes 119 with vinyl isocyanides 120 to form substituted isoquinolines 121 (Scheme 39) [129]. Both α,α-disubstituted aromatic oximes (products 121a,b,e–h) and unsubstituted (R2 = R3 = H, products 121c,d) undergo the reaction successfully. The

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• –84% yields (Scheme 59) [97]. The Ugi-type multicomponent reactions between imines, carboxylic acids, and isocyanides, and Mannich-type reactions between iminium and carbonyl groups have found many applications in organic synthesis [108]. Che’s group employed the methodology of oxidation of an amine

The reaction of arylmethyl isocyanides and arylmethylamines with xanthate esters: a facile and unexpected synthesis of carbamothioates

• Narasimhamurthy Rajeev,
• Toreshettahally R. Swaroop,
• Ahmad I. Alrawashdeh,
• Shofiur Rahman,
• Abdullah Alodhayb,
• Seegehalli M. Anil,
• Kuppalli R. Kiran,
• Chandra,
• Paris E. Georghiou,
• Kanchugarakoppal S. Rangappa and
• Maralinganadoddi P. Sadashiva

Beilstein J. Org. Chem. 2020, 16, 159–167, doi:10.3762/bjoc.16.18

• hydride-mediated reaction of arylmethyl isocyanides with xanthate esters in DMF is reported. The products thus obtained were compared with the carbamothioates obtained by the sodium hydride-mediated condensation of the corresponding benzylamines and xanthate esters in DMF. To account for these unexpected

• reactions, a mechanism is proposed in which the key steps are supported by quantum chemical calculations. Keywords: benzylamines; carbamothioates; density functional theory; intrinsic reaction coordinate analysis; isocyanides; sodium hydride; xanthate esters; Introduction Carbamothioates (thiocarbamates

• reported the synthesis of thiazoles from xanthate esters [31]. In continuation of this ongoing work, we planned to synthesize 5-alkoxy-4-arylthiazoles 3 by the sodium hydride/DMF-mediated reaction of arylmethyl isocyanides 2 with S-alkyl xanthate esters 1 or O-aryl/O-alkyl dithiocarbonates. Unexpectedly

Combining the Ugi-azide multicomponent reaction and rhodium(III)-catalyzed annulation for the synthesis of tetrazole-isoquinolone/pyridone hybrids

• Gerardo M. Ojeda,
• Prabhat Ranjan,
• Pavel Fedoseev,
• Lisandra Amable,
• Upendra K. Sharma,
• Daniel G. Rivera and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2019, 15, 2447–2457, doi:10.3762/bjoc.15.237

• compounds. As shown in Scheme 2, the design of the tetrazolic substrate included the incorporation of an N-acylaminomethyl moiety enabling the further metal-catalyzed transformations mediated by a C–H activation process. The method comprises the initial Ugi-azide-4CR – in which several isocyanides and

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

A novel three-component reaction between isocyanides, alcohols or thiols and elemental sulfur: a mild, catalyst-free approach towards O-thiocarbamates and dithiocarbamates

• András György Németh,
• György Miklós Keserű and
• Péter Ábrányi-Balogh

Beilstein J. Org. Chem. 2019, 15, 1523–1533, doi:10.3762/bjoc.15.155

• been developed between isocyanides, sulfur and alcohols or thiols under mild reaction conditions to afford O-thiocarbamates and dithiocarbamates in moderate to good yields. The one-pot reaction cascade involves the formation of an isothiocyanate intermediate, thus a catalyst-free synthesis of

• isothiocyanates, as valuable building blocks from isocyanides and sulfur is proposed, as well. The synthetic procedure suits the demand of a modern organic chemist, as it tolerates a wide range of functional groups, it is atom economic and easily scalable. Keywords: ditihiocarbamate; elemental sulfur

• yield [70]. In certain cases, sulfur can be trapped by in situ generated carbenes to afford O-thiocarbamates [71][72]. Thioureas and S-thiocarbamates are also accessible through multicomponent reactions starting from isocyanides and sulfur [73][74][75]. The cumbersome synthesis of isothiocyanates from