Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

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

• dendrimers were grown on graphene nanosheets for catalyzing the reaction using highly active Pd-Co bimetallic nanoparticles under copper and solvent-free conditions at room temperature. K2CO3 was found to be the suitable base which provided a relatively good yield (Scheme 28) [41]. The graphite sheets could

New advances in asymmetric organocatalysis

• Radovan Šebesta

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

• nitromethane to β-silyl α,β-unsaturated carbonyl compounds catalyzed by bifunctional squaramide catalysts are effective under solvent-free conditions [26]. Zhai and Du demonstrated that asymmetric [3 + 2] annulation reactions of 2-isothiocyanato-1-indanones with barbiturate-based olefins are efficiently

Solvent-free synthesis of enantioenriched β-silyl nitroalkanes under organocatalytic conditions

• Akhil K. Dubey and
• Raghunath Chowdhury

Beilstein J. Org. Chem. 2021, 17, 2642–2649, doi:10.3762/bjoc.17.177

• -unsaturated carbonyl compounds catalyzed by bifunctional squaramide catalysts has been developed. This methodology offers both enantiomers of β-silyl nitroalkanes in good to excellent yields (up to 92%) and enantioselectivities (up to 97.5% ee) under solvent-free conditions at room temperature. Control

• organosilanes [29][37][38], we present herein an organocatalyzed conjugate addition reaction of nitromethane to β-silyl enones to afford chiral β-silyl nitroalkanes (Scheme 1). Notably, the developed method was not only carried out under solvent-free conditions at room temperature but was found to be tolerant

• solvent-free conditions, and was complete within 24 h without affecting the enantioselectivity of product 3a (Table 1, entry 10). Reducing the loading of nitromethane (2) to 5 equivalents, a slight drop in yield (82%) of product 3a was observed whereas the enantioselectivity (97% ee) remained the same

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

• Michael additions of aldehydes to nitroalkenes both under solvent-free conditions and in solution. The N-sulfinylurea catalyst was more efficient than the corresponding thiourea. For some substrates, enantioselectivities reached 98% ee. The stereogenic center on the sulfur did not have a considerable

• have evaluated the suitability of these catalysts under solvent-free conditions. With the help of DFT calculations, we elucidated the mode of action of these catalysts. Results and Discussion Synthesis of catalysts We have started the synthesis of the catalysts from Boc-protected (S)-prolinol (1), from

• ). Michael additions under solvent-free reaction conditions To evaluate the applicability of the new catalysts C1 and C2, we decided to test them in the Michael addition under solvent-free conditions. Ball-milling experiments were conducted in a mixer mill, in which the milling vessels perform radial

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• -disubstituted-anthracenes from bis(dihexyloxyphenyl)arylmethanes or diveratrylmethanes and aromatic acylals [44]. In the first step, reaction between aromatic aldehydes 49 and acetic anhydride (50) promoted by Bi(OTf)3 under solvent-free conditions afforded aromatic acylals 51 (Scheme 11). In the next two steps

• -free conditions (Scheme 43) [79]. The authors used various heteroaromatic aldehydes and substituted aromatic aldehydes containing electron-donating and electron-withdrawing substituents, to obtain the ortho adducts 188 in variable yields (14–74%). The use of pyridine-3-carbaldehyde and 2,4,5

• -workers [77] provided better results. In a related approach, Estévez-Braun and co-workers synthesized dibenzo[a,h]anthracene-12,13-diones 188 from 2-hydroxy-1,4-naphthoquinone (186), β-naphthol (181), and aromatic aldehydes 187 through a multicomponent reaction that used InCl3 as catalyst under solvent

Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

• Susanne M. Fischer,
• Simon Renner,
• A. Daniel Boese and
• Christian Slugovc

Beilstein J. Org. Chem. 2021, 17, 1689–1697, doi:10.3762/bjoc.17.117

• triphenylphosphine (TPP) in catalyzing oxa-Michael additions. A matrix consisting of three differently strong Michael acceptors and four alcohols of varying acidity was used to assess the activity of the three catalysts. All test reactions were performed with 1 mol % catalyst loading, under solvent-free conditions

• highlight that solvent-free conditions are particularly effective and allow for reducing the catalyst loading by the factor of 10, thereby obtaining a higher share of 3dia and full conversion towards 3dic. Interestingly, the catalytic activity of TPP in reactions with 3 as the Michael acceptor is only

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

• reductive elimination occurs in the presence of base to achieve the desired product 119 (Scheme 36) [59]. Direct arylation of disubstituted triazoles 123 with aryl halides 124 using a Pd/C catalyst under solvent-free conditions to give fully decorated triazoles 125 was reported by Farinola et al. Different

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• under solvent-free conditions was carried out, using sodium carbonate as base promoter. The resulting dimethyl 2-(1-aminoalkyl)malonates 50 were obtained in moderate to good yields as single diastereoisomers in all cases except for aromatic aldimines. Compounds 50 could be easily transformed

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• cyclization reaction of allyl bromide (228) with a carbonyl compound promoted by BBIMBr/SnBr2 complex under solvent-free conditions has been explored [97]. The mechanism of the reaction was shown to include a Barbier reaction of allyl bromide with an aldehyde in the presence of SnBr3 and a quaternary ammonium

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

• irradiation under solvent-free conditions. The library of compounds proved to be active as xanthine oxidase inhibitors with the most potent molecule showcasing IC50 = 4 μM (Scheme 21). 5 Pyrroles Pyrroles are five-membered heterocycles consisting of four carbon atoms and a nitrogen atom. The pyrrole ring is

• construction of dihydropyrimidinones 78 utilizing a three-component reaction of acyclic 1,3-diketones 54, urea/thiourea (77) and aldehyde 5 exploring La2O3 as catalyst under microwave irradiation under solvent-free conditions with good functional group tolerance and excellent yields (Scheme 28). The reaction

• first time reported a microwave-assisted four-component domino reaction involving acyclic 1,3-diketones 54, amines 32, diethyl malonate (126) and triethyl orthoformate (111) for the synthesis of substituted pyridone derivatives 127 at 120 °C under catalyst- and solvent-free conditions. The reaction

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• in >97% yield into liquid hydrocarbon (alkane) products having a narrow distribution of the molecular weight (960–1130 g⋅mol−1) under 11.7 bar H2 at 300 °C and solvent-free conditions [146]. The pyrolysis oils produced may be used as lubricants, waxes or further processed into detergents and

An atom-economical addition of methyl azaarenes with aromatic aldehydes via benzylic C(sp³)–H bond functionalization under solvent- and catalyst-free conditions

• Divya Rohini Yennamaneni,
• Vasu Amrutham,
• Krishna Sai Gajula,
• Rammurthy Banothu,
• Murali Boosa and
• Narender Nama

Beilstein J. Org. Chem. 2020, 16, 3093–3103, doi:10.3762/bjoc.16.259

• 19, Kamala Nehru Nagar, Ghaziabad, UP-201002, India 10.3762/bjoc.16.259 Abstract A convenient practical approach for the synthesis of 2-(pyridin-2-yl)ethanols by direct benzylic addition of azaarenes and aldehydes under catalyst- and solvent-free conditions is reported. This reaction is metal-free

• azaarene derivatives under neat conditions through a highly atom-economical pathway. To evaluate the preparative potential of this process, gram-scale reactions were performed up to a 10 g scale. Keywords: aldehydes; azaarenes; benzylic addition; green chemistry; solvent-free conditions; Introduction

• , variations in the absorption, an inadequate penetrating ability of the radiation into the reaction medium, and further reflection of the microwaves. Nevertheless, the solvent was water, which required long extraction processes compared to solvent-free conditions. Castro and co-workers have also reported the

Deoxyfluorination of acyl fluorides to trifluoromethyl compounds by FLUOLEAD^®/Olah’s reagent under solvent-free conditions

• Yumeng Liang,
• Akihito Taya,
• Zhengyu Zhao,
• Norimichi Saito and
• Norio Shibata

Beilstein J. Org. Chem. 2020, 16, 3052–3058, doi:10.3762/bjoc.16.254

• the formation of trifluoromethyl compounds from acyl fluorides has been developed. The combination of FLUOLEAD® and Olah’s reagent in solvent-free conditions at 70 °C initiated the significant deoxyfluorination of the acyl fluorides and resulted in the corresponding trifluoromethyl products with high

• herein report the efficient deoxyfluorination protocol of acyl fluorides to the trifluoromethyl compounds using FLUOLEAD® (Scheme 1e). The key to the successful transformation is the use of FLUOLEAD® combined with Olah’s reagent [36] in solvent-free conditions. A wide variety of acyl fluorides involving

• reaction conditions). The investigation of a range of parameters showed that the best results were achieved by the combination of 3 equiv FLUOLEAD® and 5 equiv nHF·pyridine in solvent-free conditions at 70 °C for 24 h, providing the product 4-(trifluoromethyl)-1,1'-biphenyl (2a) in 99% 19F NMR yield (Table

Regioselective synthesis of heterocyclic N-sulfonyl amidines from heteroaromatic thioamides and sulfonyl azides

• Vladimir Ilkin,
• Vera Berseneva,
• Tetyana Beryozkina,
• Tatiana Glukhareva,
• Lidia Dianova,
• Wim Dehaen,
• Eugenia Seliverstova and
• Vasiliy Bakulev

Beilstein J. Org. Chem. 2020, 16, 2937–2947, doi:10.3762/bjoc.16.243

• have found that 1-butyl-1,2,3-triazole-4-carbothioamide (1c) reacts well with benzenesulfonyl azide (2c) in various solvents to form the desired 1-butyl-1,2,3-N-sulfonyl amidine 3n in diverse solvents such as n-butanol, n-propanol, toluene, ethanol, water and even under solvent-free conditions (see

• Table 1 for the yields and other circumstances). From these data we can conclude that the yield of the final product is optimal for the reaction under solvent-free conditions. 1-Butyl-1,2,3-triazole 1с reacts faster than 1,2,3-triazole-4-carbothioamide 1f while using a lower amount of a sulfonyl azide

• (Table 1, entry 11 and Table 2, entry 14). Thus solvent-free conditions, a temperature of 88 °C and a thioamide/azide ratio of 1:2.5 are optimal to prepare N-sulfonyl amidine 1c (entry 11, Table 1). Next, these optimized conditions were used for the synthesis of a small library of 1-alkyl-1,2,3-triazoles

Ultrasound-assisted Strecker synthesis of novel 2-(hetero)aryl-2-(arylamino)acetonitrile derivatives

• Emese Gal,
• Luiza Gaina,
• Hermina Petkes,
• Alexandra Pop,
• Castelia Cristea,
• Gabriel Barta,
• Dan Cristian Vodnar and
• Luminiţa Silaghi-Dumitrescu

Beilstein J. Org. Chem. 2020, 16, 2929–2936, doi:10.3762/bjoc.16.242

• using “green” solvents, for example, low vapor pressure solvents such as ionic liquids [3], low volatile solvents such as glycerol, ethylene glycol and its oligomers, or nontoxic water solvent, as well as in heterogeneous media under solvent-free conditions [4]. Other advantages induced by sonication

One-pot multicomponent green Hantzsch synthesis of 1,2-dihydropyridine derivatives with antiproliferative activity

• Giovanna Bosica,
• Kaylie Demanuele,
• José M. Padrón and
• Adrián Puerta

Beilstein J. Org. Chem. 2020, 16, 2862–2869, doi:10.3762/bjoc.16.235

• , and the mechanism depends much on the identity of the substrates and the reaction conditions used [18]. Cao and collaborators have managed to synthesize the 1,2-dihydropyridine (1,2-DHP) regioisomer as the main product through the Hantzsch synthesis at room temperature and solvent-free conditions

• included room temperature, a stoichiometric molar ratio of the reactants, using 40 wt % PW loaded on alumina under solvent-free conditions. These conditions satisfied the green protocol we were aiming for. Therefore, from this stage we moved onto the next one by changing the substrates to explore the

The B & B approach: Ball-milling conjugation of dextran with phenylboronic acid (PBA)-functionalized BODIPY

• Patrizia Andreozzi,
• Lorenza Tamberi,
• Elisamaria Tasca,
• Gina Elena Giacomazzo,
• Marta Martinez,
• Mirko Severi,
• Marco Marradi,
• Stefano Cicchi,
• Sergio Moya,
• Giacomo Biagiotti and
• Barbara Richichi

Beilstein J. Org. Chem. 2020, 16, 2272–2281, doi:10.3762/bjoc.16.188

• , Poland 10.3762/bjoc.16.188 Abstract Mechanochemistry is an emerging and reliable alternative to conventional solution (batch) synthesis of complex molecules under green and solvent-free conditions. In this regard, we report here on the conjugation of a dextran polysaccharide with a fluorescent probe, a

• reactions, and even in nanomaterials preparation [1][2][3][4][5]. Indeed, solid-state mechanochemical methodologies are a viable alternative to traditional syntheses in solution [4] for the preparation of complex molecules, either under solvent-free conditions, named ‘neat grinding’, or in nearly solvent

• short reaction time, reactant economy, higher degree of functionalization, and solvent-free conditions, compared to solution-based routes are discussed. The dextran mechanochemically conjugated to PBA-BODIPY (Dex-1b, Figure 1) formed nanoparticles through self-assembly retaining the fluorescent

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

• ) complex 123 as an endo-coordinated complex at the concave side. The complex 123a was prepared through the metalation of sumanene involving ligand exchange with a cyclopentadienyl (Cp) group of ferrocene by heating in the presence of Al powder and AlCl3 under solvent-free conditions followed by a counter

Preparation of 2-phospholene oxides by the isomerization of 3-phospholene oxides

• Péter Bagi,
• Réka Herbay,
• Nikolett Péczka,
• Zoltán Mucsi,
• István Timári and
• György Keglevich

Beilstein J. Org. Chem. 2020, 16, 818–832, doi:10.3762/bjoc.16.75

• -membered ring. As the thermal rearrangement was only feasible under solvent-free conditions, one may assume mechanism B, which involves the formation of phospholene oxide 1 dimers, and the second molecule only assists the rearrangement similarly to mechanism A. However, according to computations, in this

Reaction of indoles with aromatic fluoromethyl ketones: an efficient synthesis of trifluoromethyl(indolyl)phenylmethanols using K₂CO₃/n-Bu₄PBr in water

• Thanigaimalai Pillaiyar,
• Masoud Sedaghati and
• Gregor Schnakenburg

Beilstein J. Org. Chem. 2020, 16, 778–790, doi:10.3762/bjoc.16.71

• (TMG), also known as Barton's base, in excellent yields (Figure 2A) [24]. Recently, Liu and co-workers reported this reaction in the presence of cesium carbonate in acetonitrile (Figure 2B) [25]. Dinuclear zinc [26], cinchonidine catalysts, and solvent-free conditions [27] have been also utilized for

Aerobic synthesis of N-sulfonylamidines mediated by N-heterocyclic carbene copper(I) catalysts

• Faïma Lazreg,
• Marie Vasseur,
• Alexandra M. Z. Slawin and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2020, 16, 482–491, doi:10.3762/bjoc.16.43

• reaction performed in air, using solvent-free conditions and in the absence of any additive. Results and Discussion [Cu(ICy)2]BF4 (1), [Cu(IPr)(ICy)]BF4 (2) and [Cu(IPr)(Pt-Bu3)]BF4 (3) were initially selected as optimum candidates [22]. This class of catalysts was expanded through the synthesis of the

• % conversion to the desired product was observed using the homoleptic cationic MIC (mesoionic carbene) complex 6 (Table 1, entry 6). For complexes 1–5, the conversion proved modest and ranged between 42 and 49% (Table 1, entries 1–5). Subsequently, solvent-free conditions were investigated (Table 1, entries 7

• 6 was also shown to be active in water and in 1,4-dioxane. Based on these results, a reaction scope was conducted under solvent-free conditions, in air, using 1 mol % of [Cu(Triaz)2]BF4 6 (Scheme 3). Functionalised azides were reacted with phenylacetylene and diisopropylamine resulting in good to

Oligomeric ricinoleic acid preparation promoted by an efficient and recoverable Brønsted acidic ionic liquid

• Fei You,
• Xing He,
• Song Gao,
• Hong-Ru Li and
• Liang-Nian He

Beilstein J. Org. Chem. 2020, 16, 351–361, doi:10.3762/bjoc.16.34

• oligomeric ricinoleic acid from ricinoleic acid under solvent-free conditions. The reaction parameters containing reaction temperature, vacuum degree, amount of catalyst and reaction time were optimized and it was found that the reaction under the conditions of 190 °C and 50 kPa with 15 wt % of the [HSO3

• undergo esterification, providing the oligomeric ricinoleic acid with different oligomerization degree. Conclusion To conclude, a highly efficient Brønsted acidic IL catalyst [HSO3-BDBU]H2PO4 was developed for the esterification of ricinoleic acid. The reaction performed well under solvent-free conditions

Microwave-assisted synthesis of 2-substituted 4,5,6,7-tetrahydro-1,3-thiazepines from 4-aminobutanol

• María C. Mollo,
• Natalia B. Kilimciler,
• Juan A. Bisceglia and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2020, 16, 32–38, doi:10.3762/bjoc.16.5

• alcohols promoted by trimethylsilyl polyphosphate (PPSE) in solvent-free conditions allowed for the synthesis of several hitherto unreported seven-membered iminothioethers bearing 2-aryl, alkenyl, aralkyl and alkyl substituents. The cyclodehydration reaction is likely to involve an SN2-type displacement

• % yield). Based on our previous experience on related heterocycles, the cyclization was performed with PPSE under solvent-free conditions (8 min, 90 °C), delivering 73% of compound 4a as the only product. As already mentioned, Wipf et al. had previously reported that cyclization of N