Efficient synthesis of 4-substituted-ortho-phthalaldehyde analogues: toward the emergence of new building blocks

• Clémence Moitessier,
• Ahmad Rifai,
• Pierre-Edouard Danjou,
• Isabelle Mallard and
• Francine Cazier-Dennin

Beilstein J. Org. Chem. 2019, 15, 721–726, doi:10.3762/bjoc.15.67

• through a reaction of furfuryl alcohol with propargyl bromide, as is referred in the study of Cao et al. (Scheme 1) [17]. As a matter of fact, a modification of the purification step was done in order to quantitatively enhance the yield. An alternative solvent-free microwave-assisted organic synthesis

New sesquiterpenoids from the South China Sea soft corals Clavularia viridis and Lemnalia flava

• Qihao Wu,
• Yuan Gao,
• Meng-Meng Zhang,
• Li Sheng,
• Jia Li,
• Xu-Wen Li,
• Hong Wang and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2019, 15, 695–702, doi:10.3762/bjoc.15.64

• temperature (4 × 1 L). The solvent-free actone extract was partitioned between Et2O and H2O. The organic phase was evaporated under reduced pressure to give a dark-red residue (1.1 g), which was subjected to a gradient silica gel column chromatography (CC) [Et2O/petroleum ether (PE), 0–100%] to yield 6

Fabrication of supramolecular cyclodextrin–fullerene nonwovens by electrospinning

• Hiroaki Yoshida,
• Ken Kikuta and
• Toshiyuki Kida

Beilstein J. Org. Chem. 2019, 15, 89–95, doi:10.3762/bjoc.15.10

• presence of an inclusion complex structure in solvent-free supramolecular solid materials at the molecular level. Although most small molecules, including CD, generally give crystalline solids after simple casting or vacuum drying [11][28][29], electrospinning of small molecules typically provides

Green synthesis of new chiral 1-(arylamino)imidazo[2,1-a]isoindole-2,5-diones from the corresponding α-amino acid arylhydrazides in aqueous medium

• Nadia Bouzayani,
• Jamil Kraїem,
• Sylvain Marque,
• Yakdhane Kacem,
• Abel Carlin-Sinclair,
• Jérôme Marrot and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2018, 14, 2923–2930, doi:10.3762/bjoc.14.271

• (Scheme 2, Table 1) in a sealed tube in the presence of Et3N and under solvent-free conditions. From green chemistry point of view, this enhanced procedure appears to be a good alternative of the precedents for the synthesis of hydrazides 3a–m [26][27][28][29]. Moreover, the phenylglycine phenylhydrazide

• -imidazo[2,1-a]isoindole-2,5(3H,9bH)-diones. Synthesis of the starting (L)-α-amino acid phenylhydrazides and 4-chlorophenylhydrazides 3a–m under solvent-free conditions. Cyclocondensation of 2-formylbenzoic acid (4) with (L)-alanine phenylhydrazide (3a). Synthesis of the nitrogenated tricyclic compounds 5a

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• synthesis of tetrahydrobenzo[a]xanthenone derivatives 48a and the four component synthesis of tetrahydrobenzo[a]acridinone derivatives 48b were performed with good to excellent yields under solvent-free conditions at 75–85 °C within short reaction times using the higher acidic/stable ILs containing

• 110 °C under solvent-free conditions. The products were produced in very short reaction times and recrystallized in ethanol to give pure 1-amidoalkyl-2-naphthols 50 (Scheme 8). The reusability of the ionic liquid catalyst 3 was also studied. For this purpose, warm acetone was used to extract the

• , catalyst 53 was utilized for the synthesis of 2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-trione derivatives 55 via a one-pot, three-component reaction of phthalhydrazide (54), aldehydes 7, and dimedone (20) or cyclohexane-1,3-dione (for R3 = H, 20) under solvent-free conditions (Scheme 9). To check the

Assembly of fully substituted triazolochromenes via a novel multicomponent reaction or mechanochemical synthesis

• Robby Vroemans,
• Yenthel Verhaegen,
• My Tran Thi Dieu and
• Wim Dehaen

Beilstein J. Org. Chem. 2018, 14, 2689–2697, doi:10.3762/bjoc.14.246

• .14.246 Abstract A new metal-free one-pot three-component procedure towards fully substituted triazolochromenes has been developed, starting from commercially available materials. Salicylaldehydes and nitroalkenes were reacted under solvent-free conditions, followed by a 1,3-dipolar cycloaddition of the

• -nitrochromenes. Because our first step is best performed solvent-free, we opted to try our own optimized solvent-free conditions for the in situ syntheses of 3-nitro-2H-chromenes, followed by the 1,3-dipolar cycloaddition in a reaction vial. Despite being a two-pot procedure, purification of the intermediate 3

Synthesis of dihydroquinazolines from 2-aminobenzylamine: N³-aryl derivatives with electron-withdrawing groups

• Nadia Gruber,
• Jimena E. Díaz and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2018, 14, 2510–2519, doi:10.3762/bjoc.14.227

• amounts of both reactants. The reaction between 2-ABA and 2-nitrohalobenzenes was chosen for the initial optimization of the experimental conditions, whose results are collected in Table 1. No reaction was observed with 2-nitrochlorobenzene after 8 h either in solvent-free conditions at 125 °C or using

The mechanochemical synthesis of quinazolin-4(3H)-ones by controlling the reactivity of IBX

• Md Toufique Alam,
• Saikat Maiti and
• Prasenjit Mal

Beilstein J. Org. Chem. 2018, 14, 2396–2403, doi:10.3762/bjoc.14.216

• intramolecular control. At maximum contact of the reacting substances, i.e., under solvent-free mechanochemical conditions, 2-aminobenzamides, aryl-, alkylaldehydes and the iodine(V) reagent o-iodoxybenzoic acid (IBX) led to substituted quinazolin-4(3H)-one derivatives in fair yields. Keywords: ball-mill

• ; contact explosive; IBX; mechanochemical synthesis; quinazolin-4(3H)-one; Introduction An iodine and ammonia mixture is a well-known contact explosive due to formation of NI3 [1]. Similarly, hypervalent iodines as oxidizing compounds [2] react violently with amines under solvent-free conditions [3

• constructions [4][6]. Mechanochemical conditions such as ball milling are considered to be one of the premium techniques in solvent-free synthesis [7]. Under these conditions, maximum concentration is expected to put those systems under high stress and therefore violent exothermic reactions or even explosions

Bi-mediated allylation of aldehydes in [bmim][Br]: a mechanistic investigation

• Mrunesh Koli,
• Sucheta Chatterjee,
• Subrata Chattopadhyay and
• Dibakar Goswami

Beilstein J. Org. Chem. 2018, 14, 2198–2203, doi:10.3762/bjoc.14.193

• Barbier-type allylations of carbonyls have been reported in organic solvents [28][29][30], water [31] or under solvent-free conditions [32][33]. The solvent free synthetic procedure required a large excess (4–8 equiv) of Bi metal [33] whereas, the reactions in water or in organic solvents required either

Synthesis of pyrimido[1,6-a]quinoxalines via intermolecular trapping of thermally generated acyl(quinoxalin-2-yl)ketenes by Schiff bases

• Svetlana O. Kasatkina,
• Ekaterina E. Stepanova,
• Maksim V. Dmitriev,
• Ivan G. Mokrushin and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2018, 14, 1734–1742, doi:10.3762/bjoc.14.147

• 3-acylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)-triones react regioselectively with Schiff bases under solvent-free conditions to form pyrimido[1,6-a]quinoxaline derivatives in good yields. Keywords: acyl(quinoxalin-2-yl)ketenes; cycloaddition; pyrimido[1,6-a]quinoxalines; Schiff bases; thermolysis

• compounds deemed to be reversible. Performing the reaction under solvent-free conditions at the onset decarbonylation temperature (Table 1) exceeded our expectations and gave the best yields of the target compound 3a (Table 2, entry 6). Being inspired by the optimization results obtained, we examined the

• , Figure 6; CCDC 1834012, Figure 7). Conclusion We have developed a facile synthesis of pyrimido[1,6-a]quinoxaline derivatives via the intermolecular trapping of thermally generated acyl(quinoxalin-2-yl)ketenes by Schiff bases. The reaction proceeds under solvent-free conditions without any additives and

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• the thiolysis of alkyl and aryl epoxides under solvent-free conditions with 5 mol % of catalyst loading, the activity was highly dependent of the nature of the acid or base catalyst employed. The Lewis acid InCl3 and the Brønsted base K2CO3 provided superior yields and reaction rates in comparison to

• their corresponding analogs (Brønsted acid p-TsOH and Lewis base n-Bu3P, respectively) as shown in Scheme 2 [21]. In comparison to the reaction carried out under the same reaction conditions but in aqueous or organic media, it was found that the solvent-free reactions provided the β-hydroxy sulfides in

• thiols under solvent-free conditions as shown in Scheme 6 [26]. The reaction is compatible with both alkyl and arylthiols, with the nature of the substituent on the aromatic ring (electron donating/withdrawing) not having any influence on the reaction. Moreover, the reaction is compatible with

Recent applications of chiral calixarenes in asymmetric catalysis

• Mustafa Durmaz,
• Erkan Halay and
• Selahattin Bozkurt

Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117

• of Boc group gave the target compounds 69. The catalytic activities of these prolinamide organocatalysts based on the calix[4]arene scaffold were evaluated for the model reaction between 21 and 70. The results showed that under solvent-free conditions at −25 °C, 2 mol % catalyst 69b with two

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• either TrCl or DMTrCl, the products were recovered in 44% and 43% yields, respectively. Under solvent-free Corey conditions, rapid and chemoselective persilylation of ribonucleoside hydroxy functions was effected in a mixer ball mill (Scheme 2) [41]. Complete consumption of starting materials was

Phosphodiester models for cleavage of nucleic acids

• Satu Mikkola,
• Tuomas Lönnberg and
• Harri Lönnberg

Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68

• other nucleophile, including solvent water or hydroxide ion, is able to compete. The large ribozymes have to provide a solvent-free environment that suppresses the nucleophilic attack of the vicinal 2´-OH by intrachain H-bonding and promotes the attack of an external nucleophile by appropriate

• preorganization, or the RNA chain is locked to a conformation where intrachain in-line attack is not possible. Several approaches have been developed to simulate these conditions with small molecular models. The solvent-free environment of the catalytic core of large ribozymes has been mimicked in small molecular

Bromide-assisted chemoselective Heck reaction of 3-bromoindazoles under high-speed ball-milling conditions: synthesis of axitinib

• Jingbo Yu,
• Zikun Hong,
• Xinjie Yang,
• Yu Jiang,
• Zhijiang Jiang and
• Weike Su

Beilstein J. Org. Chem. 2018, 14, 786–795, doi:10.3762/bjoc.14.66

• . Currently, the Heck reaction is usually carried out by adding an excess of phase-transfer catalyst such as tetrabutylammonium bromide (TBAB) or tetrabutylammonium iodide (TBAI) to increase the reaction yield under both solvent-heating [19][20][21][22][23] and solvent-free conditions [24][25][26][27

• [33][34] and axitinib [35][36][37][38] (Scheme 1). Mechanochemistry as a burgeoning technique to promote solvent-free reactions has led to remarkable advances [39][40][41][42], particularly for cross-coupling reactions [43][44][45], involving Heck coupling with the aid of stoichiometric amounts of

• procedures [35][36], this mechanochemical protocol provided a solvent-free, highly efficient and tractable alternative, and the residual Pd content in the axitinib was determined to be no more than 2 ppm by ICP analysis. Conclusion In conclusion, a solvent-free, chemoselective Heck cross-coupling for the

Liquid-assisted grinding and ion pairing regulates percentage conversion and diastereoselectivity of the Wittig reaction under mechanochemical conditions

• Kendra Leahy Denlinger,
• Lianna Ortiz-Trankina,
• Preston Carr,
• Kingsley Benson,
• Daniel C. Waddell and
• James Mack

Beilstein J. Org. Chem. 2018, 14, 688–696, doi:10.3762/bjoc.14.57

• the reaction in comparison to completely solvent-free conditions. Finally, we observed that there was an effect of the dielectric constant of the solvent used in LAG on the stereochemistry of the product [27]. Although previously we were able to generate high yields of Wittig products under liquid

• the same rationale could be used in the case of our solvent-free conditions. In solution, ions are separated and stabilized by solvent molecules. Mechanistically we envision ions to start out as contact ion pairs, then solvent separated ion pairs (i.e., loose ion pairs) followed by free ion pairs

• . However, this pathway is shut down under solvent-free conditions, making everything in the system a contact ion pair. The traditional solution-based mechanism of the Wittig reaction proceeds via a four-membered oxaphosphetane intermediate. However, by incorporating the halide anion and the alkali metal

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• -assisted reactions, solvent-free conditions and the reusability of the catalyst (Table 1). Procedures are carried out as one-pot multicomponent transformations without the isolation of the intermediates formed. Therefore, with the application of nontoxic, readily available and inexpensive reagents, both

• , Samant et al. reported an ultrasound-promoted condensation catalysed by sulfamic acid [44]. As shown in Table 1, entries 39 and 40, both dichloroethane (DCE) and solvent-free conditions were tested. The catalyst worked at low temperature (28–30 °C) and the products were formed in short reaction times in

• -hydroxypropanals and cyclic secondary amines, Jha et al. achieved the synthesis of 2,2-dialkyl-3-dialkylamino-2,3-dihydro-1H-naphtho[2,1-b]pyrans under solvent-free conditions using pTSA as catalyst [75]. It is important to note, that during the reaction, 2,2-disubstituted 3-hydroxypropanals 26 decompose to

Palladium-catalyzed ortho-halogenations of acetanilides with N-halosuccinimides via direct sp² C–H bond activation in ball mills

• Zi Liu,
• Hui Xu and
• Guan-Wu Wang

Beilstein J. Org. Chem. 2018, 14, 430–435, doi:10.3762/bjoc.14.31

• . China 10.3762/bjoc.14.31 Abstract A solvent-free palladium-catalyzed ortho-iodination of acetanilides using N-iodosuccinimide as the iodine source has been developed under ball-milling conditions. This present method avoids the use of hazardous organic solvents, high reaction temperature, and long

• ], we have independently investigated the solvent-free ortho-iodination of acetanilides under ball-milling conditions [45]. In addition, the current reaction can be extended to ortho-bromination and ortho-chlorination by using the corresponding N-halosuccinimides. Herein, we report these regioselective

• products 3a and 4a were obtained in 73% and 77% yields, respectively (Scheme 4). Conclusion In summary, we have developed a solvent-free and efficient protocol to synthesize ortho-iodinated acetanilide derivatives with Pd(OAc)2 as the catalyst and N-iodosuccinimide as the halogen source under mechanical

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

• acetic acid (Scheme 1). In the same report the other regioisomers 6-trifluoromethylpyrazolo[3,4-b]pyridines 20 were obtained under multicomponent solvent-free conditions by the reaction of hydrazine 14, β-ketonitrile 15 and β-diketone 17 as an exclusive product. The structures of both the regioisomers

• have been confirmed unambiguously by HMBC, HMQC and 19F NMR studies. The authors proposed that trifluoromethyl-β-diketone exists mainly in keto form 17 under solvent-free conditions whereas under solvent-mediated conditions the enolic form 21 towards the carbonyl carbon that carries the CF3 group is

• ). Interestingly, high yields of the corresponding pyrazolo[3,4-b]pyridines 34 were obtained when reactions were carried under solvent-free microwave irradiation. The synthesized pyrazolo[3,4-b]pyridines have shown potential cytotoxic activity against cervical HeLa and prostate DU 205 cancer cell lines. A similar

Binding abilities of polyaminocyclodextrins: polarimetric investigations and biological assays

• Marco Russo,
• Daniele La Corte,
• Annalisa Pisciotta,
• Serena Riela,
• Rosa Alduina and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2017, 13, 2751–2763, doi:10.3762/bjoc.13.271

• further purification. The sodium alginate sample used (Sigma, lot 077K1583, extracted from Macrocystis pyrifera), presented an average content of mannuronic and guluronic units of 61% and 39%, respectively, and a molecular weight in the range 70–100 kDa. The AmCDs CD1–CD3 [37] were prepared by solvent

• -free aminolysis at 60 °C for 48 h of the heptakis(6-deoxy-6-iodo)-β-CD with a 140-fold mole-to-mole excess of the proper linear polyamine, i.e., 3-(N,N-dimethylamino)propylamine (A1) for CD1, bis(3-aminopropyl)methylamine (A2) for CD2 and bis-1,2-[(3-aminopropyl)amino]ethane (A3) for CD3. The products

A novel synthetic approach to hydroimidazo[1,5-b]pyridazines by the recyclization of itaconimides and HPLC–HRMS monitoring of the reaction pathway

• Dmitry Yu. Vandyshev,
• Khidmet S. Shikhaliev,
• Andrey Yu. Potapov,
• Michael Yu. Krysin,
• Fedor I. Zubkov and
• Lyudmila V. Sapronova

Beilstein J. Org. Chem. 2017, 13, 2561–2568, doi:10.3762/bjoc.13.252

• equivalent of C1-electrophile: R2COOH/T3P® [15], BrCN (R2 = NH2) [16], ArNCS/DCC (R2 = NHAr) [20]. Heterocyclization of 1-aminoimidazoles with 1,3-dicarbonyl or α,β-unsaturated carbonyl compounds (route B). Conditions: i) R1 = NH2, NHAlk, R2 = Ph, R3,4 = Alk, Ar, solvent-free [24], AcOH [25][26], R3 = Ph, R4

• = OEt, solvent-free [24]; ii) R1 = NH2, R2 = Ph, R3 = H, Me, R4 = Ar, ArCHO/MeOH/DMF [29] or R4 = H, HC(OEt)3/iPrOH [30]; iii) R1 = NH2, R2 = Ar, R3,4 = Alk, Ar, MeOH/N-methylmorpholine or DMF or AcOH [27][28], R3 = Ar, R4 = COOH, DMF [31], R3 = Ar, R4 = NMe2, AcOH/DMF [32]. Heterocyclization of 1

Exploring mechanochemistry to turn organic bio-relevant molecules into metal-organic frameworks: a short review

• Vânia André,
• Sílvia Quaresma,
• João Luís Ferreira da Silva and
• M. Teresa Duarte

Beilstein J. Org. Chem. 2017, 13, 2416–2427, doi:10.3762/bjoc.13.239

• field of supramolecular chemistry [27][28][29], for solvent-free preparation of co-crystals, and adducts [30][31][32][33][34][35][36][37][38], polymorphs [12], supramolecular aggregates [4][30][39][40][41][42], host–guest complexes [5][43][44][45], metal-organic frameworks (MOFs) [8][28][44][46][47][48

Mechanochemistry

• José G. Hernández

Beilstein J. Org. Chem. 2017, 13, 2372–2373, doi:10.3762/bjoc.13.234

• Jose G. Hernandez Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany 10.3762/bjoc.13.234 Keywords: green chemistry; mechanochemistry; organic chemistry; solvent-free; The scientific community’s general interest in using mechanical energy to trigger or

• of achieving chemical reactivity under solvent-free conditions. Additionally, the utilization of mechanochemical technology can often further simplify the posterior work-up procedures, having a deeper impact on the sustainability of the global synthetic process (reduction of waste, lower energy

Solvent-free copper-catalyzed click chemistry for the synthesis of N-heterocyclic hybrids based on quinoline and 1,2,3-triazole

• Martina Tireli,
• Silvija Maračić,
• Stipe Lukin,
• Marina Juribašić Kulcsár,
• Dijana Žilić,
• Mario Cetina,
• Ivan Halasz,
• Silvana Raić-Malić and
• Krunoslav Užarević

Beilstein J. Org. Chem. 2017, 13, 2352–2363, doi:10.3762/bjoc.13.232

• development of medicinal chemistry and demands of the pharmaceutical industry for greener and more efficient approaches to chemical synthesis [23][24][25]. In accordance with the progress of mechanochemistry in organic syntheses [26], ball milling has been successfully implemented for solvent-free CuAAC

• different copper species for the solvent-free mechanochemical CuAAC in a ball mill, we conducted a number of milling experiments where we assayed catalytic action of most commonly used copper(0), copper(I) and copper(II) catalysts. Mechanochemical reactions were compared to traditional solvent-based

• procedures, CuAAC reactions proved to be more efficient under solvent-free ball-milling conditions, with ca. 15-fold increase in yields of products 5 and 8. Tested mechanochemical methods showed the same dependence of reactivity to the p-substituent as reactions in solution, H < Cl < Br < I, but the

A mechanochemical approach to access the proline–proline diketopiperazine framework

• Nicolas Pétry,
• Hafid Benakki,
• Eric Clot,
• Pascal Retailleau,
• Farhate Guenoun,
• Fatima Asserar,
• Chakib Sekkat,
• Thomas-Xavier Métro,
• Jean Martinez and
• Frédéric Lamaty

Beilstein J. Org. Chem. 2017, 13, 2169–2178, doi:10.3762/bjoc.13.217

• . Subsequently, the mechanocoupling of hindered proline amino acid derivatives was developed to provide proline–proline dipeptides under solvent-free conditions. A deprotection–cyclization sequence yielded the corresponding diketopiperazines that were obtained with a high stereoselectivity which could be

• filtration of the catalytic system. 12 was engaged without further purification in a coupling reaction with Z-proline (5) and Boc-proline (6), in the solvent-free conditions described above. In both cases, the dipeptides 13 and 14 were obtained in good yields (78 and 61%, respectively). Deprotection followed