Solvent-free and room temperature synthesis of 3-arylquinolines from different anilines and styrene oxide in the presence of Al₂O₃/MeSO₃H

• Hashem Sharghi,
• Mahdi Aberi,
• Mohsen Khataminejad and
• Pezhman Shiri

Beilstein J. Org. Chem. 2017, 13, 1977–1981, doi:10.3762/bjoc.13.193

• been developed in the presence of Al2O3/MeSO3H via one-pot reaction of anilines and styrene oxide. This methodology provides very rapid access to 3-arylquinolines in good to excellent yields under solvent-free conditions at room temperature in air. Keywords: 3-arylquinolines; Al2O3; MeSO3H; one-pot

• reaction; solvent-free conditions; Introduction Quinoline derivatives have received considerable interest because they are found in numerous natural products with many biological activities. They have also played an important role in medicinal chemistry due to their pharmacological properties [1][2][3][4

• styrene oxide at room temperature under solvent-free conditions (Scheme 1). Scheme 1 briefly compares the procedure reported by Wang and co-workers and our method. As it can be seen, the reaction can be performed under very short reaction time and low temperature. Results and Discussion To exploit

Solid-state mechanochemical ω-functionalization of poly(ethylene glycol)

• Michael Y. Malca,
• Pierre-Olivier Ferko,
• Tomislav Friščić and
• Audrey Moores

Beilstein J. Org. Chem. 2017, 13, 1963–1968, doi:10.3762/bjoc.13.191

• -long solvent-based reaction conditions [19][40]. Our results also show that solvent-free conditions for the post-functionalization of native PEG is a good avenue to prevent chain lengthening, a known limitation of solvent-based techniques. Finally, our method is advantageous over solvent-based ones, as

High-speed vibration-milling-promoted synthesis of symmetrical frameworks containing two or three pyrrole units

• Marco Leonardi,
• Mercedes Villacampa and
• J. Carlos Menéndez

Beilstein J. Org. Chem. 2017, 13, 1957–1962, doi:10.3762/bjoc.13.190

• ) may be hampered by steric hindrance, since this is the only case where R3 is different from H. In the cases of 2-furyl methyl ketone and 2-thienyl methyl ketone, the reason for the lower reactivity under solvent-free conditions may be the stabilization of the intermediate enol via intramolecular

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• -free conditions were performed using a combination of (S)-binam-L-Pro (A, 5 mol %) and benzoic acid (10 mol %) as organocatalyst [49]. Juaristi and co-workers investigated the mechanistic aspects of α,α-dipeptide derivatives of a (S)-proline- (A′)-catalyzed asymmetric aldol reaction (Scheme 2b) under

• and the products were obtained in the yield up to 98% within 10 min (Scheme 1) [48]. However, the asymmetric version of a mechanochemical aldol condensation reaction was reported by Guillena and Nájera with co-workers (Scheme 2a) in 2008. Reactions between various ketones and aldehydes under solvent

Selective enzymatic esterification of lignin model compounds in the ball mill

• Ulla Weißbach,
• Saumya Dabral,
• Laure Konnert,
• Carsten Bolm and
• José G. Hernández

Beilstein J. Org. Chem. 2017, 13, 1788–1795, doi:10.3762/bjoc.13.173

• diameter) [9], demonstrated to efficiently mediate the enzymatic kinetic resolution of secondary alcohols under solvent-free conditions in both mixer and planetary ball mills (Scheme 1b) [10]. Interestingly, this latter lipase (a commercial preparation known as Novozyme 345, hereinafter referred as CALB

Mechanochemical N-alkylation of imides

• Anamarija Briš,
• Mateja Đud and
• Davor Margetić

Beilstein J. Org. Chem. 2017, 13, 1745–1752, doi:10.3762/bjoc.13.169

• . Reactions under solvent-free conditions in a ball mill gave good yields and could be put in place of the classical solution conditions. The method is general and can be applied to various imides and alkyl halides. Phthalimides prepared under ball milling conditions were used in a mechanochemical Gabriel

• found to be often advantageous over the reaction carried out by standard procedure in solvent, either by shorter reaction time, less vigorous conditions or better yields. Another advantage of solvent-free conditions is the circumvention of the problematic low solubility of some of the substrates

• deprotonation of the imides with pKa values at least within the range of 8.3–9.9 units [30] under ball milling conditions. Deprotonation of phthalimide in solution is usually carried out with the use of bases stronger than K2CO3 [31] and this difference in reactivity in comparison to solvent free conditions has

An efficient Pd–NHC catalyst system in situ generated from Na₂PdCl₄ and PEG-functionalized imidazolium salts for Mizoroki–Heck reactions in water

• Nan Sun,
• Meng Chen,
• Liqun Jin,
• Wei Zhao,
• Baoxiang Hu,
• Zhenlu Shen and
• Xinquan Hu

Beilstein J. Org. Chem. 2017, 13, 1735–1744, doi:10.3762/bjoc.13.168

• -PEG1900-Im was heated with various organic bromides (2-(bromomethyl)pyridine, benzyl bromide and 1-(bromomethyl)naphthalene) to generate the corresponding imidazolium salts L1–L3 under solvent-free conditions. All imidazolium salts were water-soluble and air-stable. The resulted salts L1–L3 were

Mechanochemical enzymatic resolution of N-benzylated-β³-amino esters

• Mario Pérez-Venegas,
• Gloria Reyes-Rangel,
• Adrián Neri,
• Jaime Escalante and
• Eusebio Juaristi

Beilstein J. Org. Chem. 2017, 13, 1728–1734, doi:10.3762/bjoc.13.167

• quite acceptable. On the other hand, no product was detected after the third cycle. To evaluate the denaturalization of the enzyme provoked by the milling process, a sample of fresh catalyst was milled for 1 h at 15 Hz under solvent-free conditions and in the presence of a LAG additive, finding that

• presents a slight decrease in ee compared with the resolution reaction using the milled enzyme under solvent-free conditions. This observation suggests that the LAG additive increases to some extent the degree of denaturation of the enzyme, reducing the enantiodiscrimination (ee = 91%) although maintaining

• additive (Table 4, entry 1) a slight decrease in yield was observed when 3 equivalents of substrate (and no LAG additive) were used to carry out the reaction (Table 4, entry 2). Nevertheless, the hydrolysis still proceeds with excellent ee (93%). This result confirms that under solvent-free conditions a

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• heating, ultrasonication and solvent-free conditions alleviated the drawbacks to a major extent [56][57][58][59][60][61]. One such useful strategy include manganese dioxide (MnO2)-mediated oxidative aromatization of 1,4-DHP 45 to afford substituted pyridine derivatives 46 under microwave conditions

Phenylsilane as an effective desulfinylation reagent

• Wanda H. Midura,
• Aneta Rzewnicka and
• Jerzy A. Krysiak

Beilstein J. Org. Chem. 2017, 13, 1513–1517, doi:10.3762/bjoc.13.150

• silane procedure led to the single diastereomer 7a. In this case determination of the relative configuration as trans was based on a high coupling constant 3JP-H = 17.0 Hz, which evidenced retention of configuration during the desulfinylation process (Scheme 2). The reaction conducted under solvent-free

• conditions with a large excess of silyl reagent (procedure 1) occurred with full conversion of the cyclopropanes, although some problems with the isolation of the product due to an excess of silane induced a modification of the reduction procedure. The gain of using THF as a solvent [17] (procedure 2) let us

Mechanochemical borylation of aryldiazonium salts; merging light and ball milling

• José G. Hernández

Beilstein J. Org. Chem. 2017, 13, 1463–1469, doi:10.3762/bjoc.13.144

• spectroscopy. This time trace quantities of product 3a were detected (Table 1, entry 5). This interesting result under solvent-free conditions encouraged performing the light irradiation accompanied by milling to improve mixing and to increase the surface exposure of the reaction mixture. In a following set of

Continuous-flow processes for the catalytic partial hydrogenation reaction of alkynes

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

Beilstein J. Org. Chem. 2017, 13, 734–754, doi:10.3762/bjoc.13.73

• either using the Lindlar catalyst (84.6%) under smooth reaction conditions (298 K, 1 bar H2, Table 1, entry 1) or 16.2 wt % CeO2@TiO2 (97%), the latter resulting in a very high STY for 1a (18.86 kg L−1 h−1) under solvent-free conditions (Table 1, entry 2) [119]. Use of cerium oxide is certainly

Effect of the ortho-hydroxy group of salicylaldehyde in the A³ coupling reaction: A metal-catalyst-free synthesis of propargylamine

• Sujit Ghosh,
• Kinkar Biswas,
• Suchandra Bhattacharya,
• Pranab Ghosh and
• Basudeb Basu

Beilstein J. Org. Chem. 2017, 13, 552–557, doi:10.3762/bjoc.13.53

• achieved in the first two solvents (85–88%), the use of ethanol resulted in a low yield (47%). Thus the A3 coupling of salicylaldehyde, phenylacetylene and morpholine can be achieved under solvent-free conditions as well as in solvents like toluene or acetonitrile with the formation of the coupled product

• only metal-catalyst-free approach from acetylene carboxylic acids that are difficultly accessible and with low atom economy. Thus the present reaction from easily available A3 components leading to the formation of propargylamine under metal-catalyst-free and solvent-free conditions could attract the

The synthesis of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides by the microwave-assisted Pudovik reaction

• Erika Bálint,
• Ádám Tajti,
• Anna Ádám,
• István Csontos,
• Konstantin Karaghiosoff,
• Mátyás Czugler,
• Péter Ábrányi-Balogh and
• György Keglevich

Beilstein J. Org. Chem. 2017, 13, 76–86, doi:10.3762/bjoc.13.10

• ][34][35][36][37][38], while in a few cases the catalysts, i.e., PTSA [39], Na [40], TEA [21] or MoO2Cl2 [41], were used under solvent-free conditions. As for the microwave (MW)-assisted additions, only two cases were reported, but the catalytic variations were carried out in kitchen MW ovens [32][42

• aniline at room temperature under solvent-free conditions (Scheme 1). Then, the reaction of N-benzylidene(butyl)amine (1a) with four different dialkyl phosphites and diphenylphosphine oxide was investigated under MW-assisted solvent-free conditions searching for the optimum temperature and reaction time

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

• extensive amount of research into continuous organic transformations by extrusion and encourage them to consider the potential that extrusion holds for continuous chemical synthesis, particularly under solvent-free conditions. Reactive extrusion (REX) Extrusion is employed most frequently in the polymer

• polymerisation reactions are typically dependent on the solvent employed, temperature and concentration [17], however, when they are conducted by extrusion, they are carried out under solvent-free conditions, which is a major advantage. It must also be noted that to carry out a reaction solvent-free, when a

• interactions upon mixing, but these did not involve the formation of a covalent bond. However, James et al. report on the formation of covalent bonds in metal-organic frameworks (MOFs) and discrete metal complexes by TSE, under solvent-free conditions or in the presence of stoichiometric amounts of MeOH [2

First DMAP-mediated direct conversion of Morita–Baylis–Hillman alcohols into γ-ketoallylphosphonates: Synthesis of γ-aminoallylphosphonates

• Marwa Ayadi,
• Haitham Elleuch,
• Emmanuel Vrancken and
• Farhat Rezgui

Beilstein J. Org. Chem. 2016, 12, 2906–2915, doi:10.3762/bjoc.12.290

• -ketoallylphosphonates from primary and secondary MBH alcohols, with or without DMAP used as additive, and under solvent-free conditions (Scheme 1, reaction 5 and Scheme 2, reaction 7). Taking into consideration the importance of aminophosphonates (vide infra), we developed in the second part of this study an efficient

• mixture conducted without any additive and under solvent-free conditions, at room temperature or at 80 °C, indicated that no reaction occurred and the starting materials were completely recovered (Table 1, entry 5). However, when 0.5 equiv of DMAP was employed under the previous conditions, the

• phosphonate 2a was isolated within 4 h in 35% yield (Table 1, entry 6). After screening several amounts of DMAP, under solvent-free conditions at 80 °C, we observed that the best yield (75%) was obtained using 1 equiv of DMAP (Table 1, entry 7). Under these reaction conditions, the allylic phosphonate 2a was

Orthogonal protection of saccharide polyols through solvent-free one-pot sequences based on regioselective silylations

• Serena Traboni,
• Emiliano Bedini and
• Alfonso Iadonisi

Beilstein J. Org. Chem. 2016, 12, 2748–2756, doi:10.3762/bjoc.12.271

• conducted in short times with the requisite silyl chloride and a very limited excess of pyridine (2–3 equivalents). Under these conditions, that can be regarded as solvent-free conditions in view of the insolubility of the polyol substrates, the reactions are faster than in most examples reported in the

• after in situ peracetylation (Table 2, entry 8). The scope of the TBAB-catalyzed silyl protection under solvent-free conditions was next examined for the regioselective attachment of TBDPS (Table 2, entries 9–13), a commonly used silyl protecting group bulkier than TBDMS and more resistant to acidic

• same time. Not unexpectedly, secondary alcohols exhibited a recalcitrant reactivity towards TBDPSCl under these solvent-free conditions, and the di-O-silylation process resulted in limited synthetic usefulness (data not shown). The scope of the solvent-free conditions was further examined in the

Selective synthesis of thioethers in the presence of a transition-metal-free solid Lewis acid

• Federica Santoro,
• Matteo Mariani,
• Federica Zaccheria,
• Rinaldo Psaro and
• Nicoletta Ravasio

Beilstein J. Org. Chem. 2016, 12, 2627–2635, doi:10.3762/bjoc.12.259

• alumina catalyst with a very low content in alumina gave excellent results in terms of both activity and selectivity also under solvent-free conditions. The reaction rate follows the electron density of the carbinol atom in the substrate alcohol and yields up to 99% and can be obtained for a wide range of

• thiols and benzylic alcohols under solvent-free conditions in excellent yields [21]. We already reported on the use of amorphous solid acid catalysts in organic synthesis. These solids are formed by dispersing a small amount of an inorganic oxide with Lewis acid nature onto the surface of silica [22]. In

• report that excellent yields can be obtained in the presence of an amorphous solid catalyst under solvent-free conditions. Results and Discussion In order to test our hypothesis we carried out the reaction of 1-(4-methoxyphenyl)ethanol (1a) and benzyl mercaptan (2a) in the presence of different solid

Efficient mechanochemical synthesis of regioselective persubstituted cyclodextrins

• Laszlo Jicsinszky,
• Marina Caporaso,
• Katia Martina,
• Emanuela Calcio Gaudino and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2016, 12, 2364–2371, doi:10.3762/bjoc.12.230

• -6-substituted cyclodextrin derivative syntheses have been effectively carried out in a planetary ball mill under solvent-free conditions. The preparation of Bridion® and important per-6-amino/thiocyclodextrin intermediates without polar aprotic solvents, a source of byproducts and persistent

• sometimes affected the reaction rate, a solvent-free synthetic method may simplify the purification of compounds 5 and 6. Conclusion Syntheses of per-6-substituted CD derivatives can be effectively carried out in a ball mill under solvent-free conditions. In many cases, ball mill preparations display a

Tunable microwave-assisted method for the solvent-free and catalyst-free peracetylation of natural products

• Manuela Oliverio,
• Paola Costanzo,
• Monica Nardi,
• Carla Calandruccio,
• Raffaele Salerno and
• Antonio Procopio

Beilstein J. Org. Chem. 2016, 12, 2222–2233, doi:10.3762/bjoc.12.214

• preferably acetic anhydride in solvent free conditions, in presence of non-toxic homogeneous catalysts such as environmental safe Lewis acids [13][14]. Moreover, the need to easily recover and reuse the catalyst, thus reducing the work-up procedure to a simple filtration, resulted in the growing use of

Silica-supported sulfonic acids as recyclable catalyst for esterification of levulinic acid with stoichiometric amounts of alcohols

• Raimondo Maggi,
• N. Raveendran Shiju,
• Veronica Santacroce,
• Giovanni Maestri,
• Franca Bigi and
• Gadi Rothenberg

Beilstein J. Org. Chem. 2016, 12, 2173–2180, doi:10.3762/bjoc.12.207

• sulfonated catalyst (1%), an equimolecular amount of reagents under solvent free conditions, and varying the temperature between 50–100 °C. Results are reported in Table 3. In all cases, the selectivity towards the esterification product 3a remained complete. A comparable yield of 3a was recovered reducing

Solvent-free synthesis of novel para-menthane-3,8-diol ester derivatives from citronellal using a polymer-supported scandium triflate catalyst

• Lubabalo Mafu,
• Ben Zeelie and
• Paul Watts

Beilstein J. Org. Chem. 2016, 12, 2046–2054, doi:10.3762/bjoc.12.193

• was used. Moreover, all the reactions were carried-out under solvent-free conditions. Reaction parameters such as temperature, reaction time and reagent molar ratio were studied towards the substrate conversion and product selectivity. Effect of reaction temperature and reaction time In order to

Microwave-assisted cyclizations promoted by polyphosphoric acid esters: a general method for 1-aryl-2-iminoazacycloalkanes

• Jimena E. Díaz,
• María C. Mollo and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2016, 12, 2026–2031, doi:10.3762/bjoc.12.190

• trimethylsilyl polyphosphate (PPSE) in solvent-free conditions allowed for the synthesis of 1-aryl-2-iminopiperidines and hitherto unreported 1-aryl-2-iminoazepanes. The cyclization reaction involves good to high yields and short reaction times, and represents a novel application of PPA esters in heterocyclic

• under certain conditions [45][46]. Using a dichloromethane solution of PPSE, compound 4a was obtained exclusively (Table 2, entries 4–6), while working under solvent-free conditions further improved the yield (Table 2, entry 7). Employing the optimized reaction conditions (neat PPSE, 30 min at 150 °C

• reaction under solvent-free conditions at 150 °C, compound 7a was obtained in modest yield (Table 4, entry 5). Significantly better results were achieved by increasing the temperature to 200 °C (Table 4, entry 6). Employing the optimized reaction conditions, we synthesized some novel 1-aryl-2-iminoazepanes

Ionic liquids as transesterification catalysts: applications for the synthesis of linear and cyclic organic carbonates

• Maurizio Selva,
• Alvise Perosa,
• Sandro Guidi and
• Lisa Cattelan

Beilstein J. Org. Chem. 2016, 12, 1911–1924, doi:10.3762/bjoc.12.181

• -value chemicals. This holds true also for enzyme-catalyzed transesterification reactions. To cite a few examples, the literature claims the use of lipase as a biocatalyst for i) the reaction of glycerol with DMC for the synthesis of glycerol carbonate (GlyC) under solvent-free conditions. A 60% yield

TMSBr-mediated solvent- and work-up-free synthesis of α-2-deoxyglycosides from glycals

• Mei-Yuan Hsu,
• Yi-Pei Liu,
• Sarah Lam,
• Su-Ching Lin and
• Cheng-Chung Wang

Beilstein J. Org. Chem. 2016, 12, 1758–1764, doi:10.3762/bjoc.12.164

• University, Taipei 106, Taiwan Department of Chemistry, National Central University, Jhongli 320, Taiwan 10.3762/bjoc.12.164 Abstract The thio-additions of glycals were efficiently promoted by a stoichiometric amount of trimethylsilyl bromide (TMSBr) to produce S-2-deoxyglycosides under solvent-free

• conditions in good to excellent yields. In addition, with triphenylphosphine oxide as an additive, the TMSBr-mediated direct glycosylations of glycals with a large range of alcohols were highly α-selective. Keywords: 2-deoxyglycosides; glycals; trimethylsilyl bromide (TMSBr); triphenylphosphine oxide (TPPO