Preparation of phosphines through C–P bond formation

• Iris Wauters,
• Wouter Debrouwer and
• Christian V. Stevens

Beilstein J. Org. Chem. 2014, 10, 1064–1096, doi:10.3762/bjoc.10.106

• also been shown to take place at room temperature in the absence of a catalyst [86][87] and even under solvent-free conditions [88]. More recently also metal complex-assisted or organocatalyzed hydrophosphinations have been reported. Several reviews focusing on hydrophosphination have been pusblished

• corresponding triflate under similar conditions [196][197]. The reaction also proceeded under solvent-free conditions with slightly higher yields [198]. A heterogeneous Pd/C catalyst has been applied as well [199][200]. The group of Glueck has reported the first asymmetric palladium-catalyzed C–P bond formation

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

• Gijs Koopmanschap,
• Eelco Ruijter and
• Romano V.A. Orru

Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50

• proved to be faster. However, a solvent-free approach also resulted in the desired β-lactams with similar results in yield, diastereoselectivity and time. Besides bicyclic systems, Ugi 4C-3CRs towards monocyclic β-lactams are also described in both organic and aqueous media. Pirrung et al. published a

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• recently, silver–NHC complexes were found to be valuable catalysts for this MCR. Their first application was reported by Wang and co-workers in 2008 [12], who developed a polystyrene-supported NHC–Ag(I) complex as an efficient catalyst for the A3-coupling under solvent-free conditions, at room temperature

Simple two-step synthesis of 2,4-disubstituted pyrroles and 3,5-disubstituted pyrrole-2-carbonitriles from enones

• Murat Kucukdisli,
• Dorota Ferenc,
• Marcel Heinz,
• Christine Wiebe and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 466–470, doi:10.3762/bjoc.10.44

• . Gratifyingly, yield and purity of pyrrole 7a increased when 6a was heated with microwaves to 250 °C under air cooling of the reaction vessel without any additive under solvent-free conditions. The results of the application of these conditions to cyanopyrrolines 6a–j are summarized in Table 1. This compound

Practical synthesis of aryl-2-methyl-3-butyn-2-ols from aryl bromides via conventional and decarboxylative copper-free Sonogashira coupling reactions

• Andrea Caporale,
• Stefano Tartaggia,
• Andrea Castellin and
• Ottorino De Lucchi

Beilstein J. Org. Chem. 2014, 10, 384–393, doi:10.3762/bjoc.10.36

• variants have been introduced to perform efficiently this reaction with regard to synthetic and industrial aspects, including protocols in aqueous media [14][15][16][17], amine-free [18] or solvent-free conditions [19]. Moreover efficient reusable Pd catalysts [20][21][22][23][24] and even palladium-free

Silica: An efficient catalyst for one-pot regioselective synthesis of dithioethers

• Samir Kundu,
• Babli Roy and
• Basudeb Basu

Beilstein J. Org. Chem. 2014, 10, 26–33, doi:10.3762/bjoc.10.5

• Samir Kundu Babli Roy Basudeb Basu Department of Chemistry, North Bengal University, Darjeeling 734013, India, Fax: +91 353 2699001 10.3762/bjoc.10.5 Abstract The development of a silica-promoted highly selective synthesis of 1,2 or 1,3-dithioethers via solvent-free one-pot tandem reactions of an

• hydrothiolation of allylic substrates in a Markovnikov fashion to afford 1,2-dithioethers in one-pot reactions. In this paper, we wish to report our investigations on the reaction of allyl halides with excess thiols promoted by silica gel, which finally constitutes distinct protocols for one-pot, solvent-free

Less reactive dipoles of diazodicarbonyl compounds in reaction with cycloaliphatic thioketones – First evidence for the 1,3-oxathiole–thiocarbonyl ylide interconversion

• Valerij A. Nikolaev,
• Alexey V. Ivanov,
• Ludmila L. Rodina and
• Grzegorz Mlostoń

Beilstein J. Org. Chem. 2013, 9, 2751–2761, doi:10.3762/bjoc.9.309

• intensive red or orange color of thioketone 1. In order to enhance the concentration of the reagents and thereby increase the rate of the reaction, experiments with liquid diazocompounds 2a,c–e,h and i and thioketone 1a were carried out under solvent-free conditions. On the other hand, reactions of solid

Multigramme synthesis and asymmetric dihydroxylation of a 4-fluorobut-2E-enoate

• James A. B. Laurenson,
• John A. Parkinson,
• Jonathan M. Percy,
• Giuseppe Rinaudo and
• Ricard Roig

Beilstein J. Org. Chem. 2013, 9, 2660–2668, doi:10.3762/bjoc.9.301

• effective as the reaction solvent instead of carbon tetrachloride, allowing 23 and 24 to be isolated safely and reproducibly at scale (>300 mmol) in moderate yield (48–53%) after Kugelrohr distillation (Scheme 4). Fluorination was attempted using a range of conditions. The solvent-free reaction developed

Triol-promoted activation of C–F bonds: Amination of benzylic fluorides under highly concentrated conditions mediated by 1,1,1-tris(hydroxymethyl)propane

• Pier Alexandre Champagne,
• Alexandre Saint-Martin,
• Mélina Drouin and
• Jean-François Paquin

Beilstein J. Org. Chem. 2013, 9, 2451–2456, doi:10.3762/bjoc.9.283

• from our solvent-free conditions, which were providing the better results, we envisioned that further optimization was possible to improve the yield (Table 2). First, temperature had an important impact on conversion. Indeed, going from 60 °C (Table 2, entry 1) to 100 °C (Table 2, entry 3) smoothly

• neutral and solvent-free conditions. To further support this hypothesis, solvent properties concerning their hydrogen bond acidity or basicity correlate well with the experimental evidence of reactivity. Investigations concerning the reaction mechanism and precise role of the three hydroxy groups of 2 for

Silica sulfuric acid: a reusable solid catalyst for one pot synthesis of densely substituted pyrrole-fused isocoumarins under solvent-free conditions

• Sudipta Pathak,
• Kamalesh Debnath and
• Animesh Pramanik

Beilstein J. Org. Chem. 2013, 9, 2344–2353, doi:10.3762/bjoc.9.269

• pyrrole-fused isocoumarins, which employs solid-supported silica sulfuric acid (SSA) as catalyst, has been developed. When the mixture of ninhydrin adducts of acetylacetone/ethyl acetoacetate and primary amines was heated on the solid surface of SSA under solvent-free conditions, the pyrrole-fused

• isocoumarins were formed in good yields. This synthetic method has several advantages such as the employment of solvent-free reaction conditions without the use of any toxic reagents and metal catalysts, the ease of product isolation, the use of a recyclable catalyst, the low cost, the easy availability of the

• starting materials, and the excellent yields of products. Keywords: green chemistry; pyrrole-fused isocoumarin; reusable solid support; silica sulfuric acid; solvent-free condition; Introduction Isocoumarins are an important class of naturally occurring lactones [1][2][3], which has attracted the

Acid, silver, and solvent-free gold-catalyzed hydrophenoxylation of internal alkynes

• Marcia E. Richard,
• Daniel V. Fraccica,
• Kevin J. Garcia,
• Erica J. Miller,
• Rosa M. Ciccarelli,
• Erin C. Holahan,
• Victoria L. Resh,
• Aakash Shah,
• Peter M. Findeis and
• Robert A. Stockland Jr.

Beilstein J. Org. Chem. 2013, 9, 2002–2008, doi:10.3762/bjoc.9.235

• ; gold; gold catalysis; hydrophenoxylation; silver-free; single component; solvent-free; Introduction The use of gold compounds to promote hydroelementation reactions has grown tremendously over the past few years [1][2][3][4][5]. Using this approach, a host of different organic substrates have been

• is focused on the elimination of solvents and additives from the synthetic methodology [10]. Thus, the design of gold catalyzed reactions that proceed under solvent-free conditions and without the addition of silver salts or acidic promoters would be of interest to those charged with designing

• -free conditions [12][13]. To this end, we have synthesized and investigated a series of arylgold compounds as single-component catalysts for hydroelementation reactions under acid, silver, and solvent-free conditions. We recently reported the synthesis of arylgold compounds using a focused microwave

A³-Coupling catalyzed by robust Au nanoparticles covalently bonded to HS-functionalized cellulose nanocrystalline films

• Jian-Lin Huang,
• Derek G. Gray and
• Chao-Jun Li

Beilstein J. Org. Chem. 2013, 9, 1388–1396, doi:10.3762/bjoc.9.155

• reaches completion after 24 h under the present conditions. At a lower reaction temperature (25 °C), the Au@HS-CNC(4.4 mol %) showed lower conversion due to an incomplete reaction. We obtained the best conversion at a higher reaction temperature (above 80 °C). Solvent-free conditions proved to be the most

• nanoparticles at 80 °C, solvent-free in air. To expand the scope of this A3-coupling, we used various aldehydes and amines as substrates under the optimized reaction conditions, and the results are summarized in Table 2. Both aromatic and aliphatic aldehydes provided the desired products in good to moderate

• vacuum, and then reused with a fresh charge of reactants for a subsequent run of reactions under identical conditions. Figure 6 demonstrates that the catalyst could be used repetitively more than 11 times without significant deactivation, suggesting its good reusability in solvent-free A3-coupling of

Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review

• Lucio Melone and
• Carlo Punta

Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146

• hydroperoxide intermediate, prolonging the free-radical chain [39][40][41]. The NHPI-activation by AQ has been also adopted by other research groups. Li and co-workers applied the NHPI/AQ system to promote the metal and solvent-free oxidation of α-isophorone to ketoisophorone, preventing the isomerization

Synthesis and physicochemical characterization of novel phenotypic probes targeting the nuclear factor-kappa B signaling pathway

• Paul M. Hershberger,
• Satyamaheshwar Peddibhotla,
• E. Hampton Sessions,
• Daniela B. Divlianska,
• Ricardo G. Correa,
• Anthony B. Pinkerton,
• John C. Reed and
• Gregory P. Roth

Beilstein J. Org. Chem. 2013, 9, 900–907, doi:10.3762/bjoc.9.103

• ethyl xanthate in ethanol under reflux. Bromination of 1 led to the key intermediate 2-bromo-5,6-dimethylbenzimidazole (2), which reacted smoothly with 3-aminopropanol to give the amine 3 in high yield and purity after extraction. The solvent-free microwave process employed was superior to traditional

Synthesis of phenanthridines via palladium-catalyzed picolinamide-directed sequential C–H functionalization

• Ryan Pearson,
• Shuyu Zhang,
• Gang He,
• Nicola Edwards and
• Gong Chen

Beilstein J. Org. Chem. 2013, 9, 891–899, doi:10.3762/bjoc.9.102

• . We commenced the study by investigating the arylation of 2-methoxybenzyl picolinamide 1 with 4-iodoanisole (2) under various conditions (Table 1) to form our desired arylated product 3. Our initial attempt under the original Pd(OAc)2-catalyzed AgOAc-promoted solvent-free condition afforded the

Expeditious, mechanochemical synthesis of BODIPY dyes

• Laramie P. Jameson and
• Sergei V. Dzyuba

Beilstein J. Org. Chem. 2013, 9, 786–790, doi:10.3762/bjoc.9.89

• Laramie P. Jameson Sergei V. Dzyuba Department of Chemistry, Texas Christian University, Fort Worth, TX 76129, USA 10.3762/bjoc.9.89 Abstract BODIPY dyes have been synthesized under solvent-free or essentially solvent-free conditions, within about 5 minutes in an open-to-air setup by using a

• pestle and mortar, with yields that are comparable to those obtained via traditional routes that typically require reaction times of several hours to days. Keywords: BODIPY; condensation; fluorescent dye; mechanochemistry; solvent-free; Introduction BODIPY dyes are fluorescent organic molecules, which

• air-sensitive nature of DBU (Table 1, entry 5). Et3N, however, appeared to give reproducible results. In contrast, inorganic bases added as solids (K2CO3 and NaOH, Table 1, entries 6 and 7, respectively) failed to give the desired product. Overall, this essentially solvent-free, 5-minute procedure can

A facile, rapid, one-pot regio/stereoselective synthesis of 2-iminothiazolidin-4-ones under solvent/scavenger-free conditions

• Murugan Sathishkumar,
• Sangaraiah Nagarajan,
• Poovan Shanmugavelan,
• Murugan Dinesh and
• Alagusundaram Ponnuswamy

Beilstein J. Org. Chem. 2013, 9, 689–697, doi:10.3762/bjoc.9.78

• based on the relative magnitude of the allylic strains developed during the course of the reaction. This is the first report wherein the impact of allylic strains in directing the regiocyclization has been noted. Keywords: 2-iminothiazolidin-4-ones; regioselective; stereoselective; solvent-free

• environmentally friendly methodologies for the synthesis of 2-iminothiazolidin-4-ones is worth attempting. In this regard, and in continuation of our recent reports on the solvent-free synthesis of amides [19][20], thioamides [21], cyclic imides [22], thiazolidin-4-ones [23], spirothiazolidin-4-ones [24], 1,2,3

• are presented below. Results and Discussion At the outset, optimization of the one-pot reaction was attempted by varying the solvents and using triethylamine as the acid scavenger (Table 1). The reaction was also attempted under solvent-free conditions. The latter was more promising in the sense that

1-n-Butyl-3-methylimidazolium-2-carboxylate: a versatile precatalyst for the ring-opening polymerization of ε-caprolactone and rac-lactide under solvent-free conditions

• Astrid Hoppe,
• Faten Sadaka,
• Claire-Hélène Brachais,
• Gilles Boni,
• Jean-Pierre Couvercelle and
• Laurent Plasseraud

Beilstein J. Org. Chem. 2013, 9, 647–654, doi:10.3762/bjoc.9.73

• of ε-caprolactone (ε-CL) and rac-lactide (rac-LA) under solvent-free conditions and using 1-n-butyl-3-methylimidazolium-2-carboxylate (BMIM-2-CO2) as precatalyst is described. Linear and star-branched polyesters were synthesized by successive use of benzyl alcohol, ethylene glycol, glycerol and

• concept was extended to the synthesis of aliphatic polycarbonates, involving the transesterification of DMC with linear alkane diols under solvent-free conditions, and based on a two-step polymerization process [50]. The high reactivity of imidazolium-2-carboxylates can be explained by their facile

• decarboxylation, thus generating active carbene species, which occurs either by heating [51] or by the addition of Na+ or K+ (NaBPh4, KPF6) [47]. In this paper, we apply this dual approach to the solvent-free ROP of ε-caprolactone and rac-lactide using 1-n-butyl-3-methylimidazolium-2-carboxylate (BMIM-2-CO2) as a

Chemoenzymatic synthesis and biological evaluation of enantiomerically enriched 1-(β-hydroxypropyl)imidazolium- and triazolium-based ionic liquids

• Paweł Borowiecki,
• Małgorzata Milner-Krawczyk and
• Jan Plenkiewicz

Beilstein J. Org. Chem. 2013, 9, 516–525, doi:10.3762/bjoc.9.56

• Pawel Borowiecki Malgorzata Milner-Krawczyk Jan Plenkiewicz Warsaw University of Technology, Faculty of Chemistry, Noakowskiego St. 3, 00-664 Warsaw, Poland 10.3762/bjoc.9.56 Abstract Racemic 1-(β-hydroxypropyl)azoles were prepared by solvent-free direct regioselective ring opening of 1,2

• oxide (1) under solvent-free conditions. The epoxide ring-opening reactions were carried for 24 h at elevated temperature (32 °C) and resulted in the formation of the appropriate alcohols (±)-3a and (±)-3b in high yields (Scheme 1). In the next step, the influence of crucial parameters in enzyme

A new synthetic access to 2-N-(glycosyl)thiosemicarbazides from 3-N-(glycosyl)oxadiazolinethiones and the regioselectivity of the glycosylation of their oxadiazolinethione precursors

• El Sayed H. El Ashry,
• El Sayed H. El Tamany,
• Mohy El Din Abdel Fattah,
• Mohamed R. E. Aly,
• Ahmed T. A. Boraei and
• Axel Duerkop

Beilstein J. Org. Chem. 2013, 9, 135–146, doi:10.3762/bjoc.9.16

• signals at δc 176.10–177.40 ppm. Anomeric carbons in both types were observed at δ 83.20–84.00 ppm. Thermal rearrangement of the S-glycosides 5–7 under solvent-free and atmospheric conditions afforded the corresponding 3-N-glycosides 8–10. The conversion was achieved in a few minutes with good to

• type II (from the four glycosylthiosemicarbazide structural isomers I–IV shown in Scheme 1) were synthesized from 3-N-(glycosyl)oxadiazolinethiones, which were accessed by new regioselective glycosylations. Additionally, 3-N-(glycosyl)oxadiazolinethiones may be prepared by a mild solvent-free thermal S

Reactions of salicylaldehyde and enolates or their equivalents: versatile synthetic routes to chromane derivatives

• Ishmael B. Masesane and
• Zelalem Yibralign Desta

Beilstein J. Org. Chem. 2012, 8, 2166–2175, doi:10.3762/bjoc.8.244

• (aq) in ethanol as reported by Mazimba and co-workers. Chalcone 9 was then oxidatively cyclized in the presence of iodine and in a solvent-free environment to give flavone (11) in 72% yield. Methyl-, methoxy- and chloro-substituted acetophenones were also well tolerated in the reaction to give the

Mechanochemistry assisted asymmetric organocatalysis: A sustainable approach

• Pankaj Chauhan and
• Swapandeep Singh Chimni

Beilstein J. Org. Chem. 2012, 8, 2132–2141, doi:10.3762/bjoc.8.240

• : ball-milling; enantioselective synthesis; mechanochemistry; organocatalysis; solvent-free; Introduction Green chemistry involves innovation in chemical research and engineering that encourages the design of processes to minimize the use and production of hazardous materials and also reduce the use of

• synthetic organic chemistry has increased considerably, due to the need for development of sustainable methodologies, and has been widely used in solvent-free non-asymmetric transformations. On the other hand, demands for the development of stereoselective synthesis of organic molecules have noticeably

• transformations assisted by mechanochemical techniques proved to be an excellent alternative to atom-economical stereoselective transformations under solvent-free reaction conditions. This review gives an overview of the solvent-free asymmetric organocatalytic transformation assisted by mechanochemical techniques

Catalyst-free and solvent-free Michael addition of 1,3-dicarbonyl compounds to nitroalkenes by a grinding method

• Zong-Bo Xie,
• Na Wang,
• Ming-Yu Wu,
• Ting He,
• Zhang-Gao Le and
• Xiao-Qi Yu

Beilstein J. Org. Chem. 2012, 8, 534–538, doi:10.3762/bjoc.8.61

• yields by a grinding method under catalyst- and solvent-free conditions. Keywords: catalyst-free; grinding; Michael addition; solvent-free; Introduction Nowadays, chemists are vigorously taking on the challenge of developing green synthetic methodologies to meet the criteria of sustainable

• , environmentally conscious development. As a result, catalyst- and solvent-free synthetic methods have attracted much interest not only for laboratory synthesis but also in chemical industry, because of reduced pollution, lower costs, mild conditions, and ease of purification. Recently, practical procedures in the

• absence of solvents and catalysts have been accomplished for greener and cleaner syntheses [1][2][3][4][5][6]. As the typical representative of solvent-free reactions, the grinding technique has been widely used in organic synthesis [7][8][9][10][11][12][13]. Compared to traditional methods, some organic

Syntheses and applications of furanyl-functionalised 2,2’:6’,2’’-terpyridines

• Jérôme Husson and
• Michael Knorr

Beilstein J. Org. Chem. 2012, 8, 379–389, doi:10.3762/bjoc.8.41

• [19][21] was tested, since it is known to be an efficient promoter of aldol condensations and Michael additions under solvent-free conditions [22][23]. Nevertheless, the treatment of furanyl-substituted aldehydes 1, 3 and 15 did not yield the targeted diketo-intermediates, but instead the chalcones 5

• hydroxide or barium hydroxide. More recently, another one-pot two-steps procedure using the environmentally benign solvent ethanol was described [24]. The reaction is based on the same mechanism as the solvent-free synthesis described above, but provides better yields. This protocol was recently used to

• ) American Chemical Society). Structure of pyrrolyl (66), thienyl (67) and bithienyl (68)-substituted complexes analogous to compound 43. PF6− counter-anions are omitted. Synthesis of furanyl-substituted terpyridines 12–14 by using Kröhnke’s method. Synthesis of terpyridines under solvent-free conditions

Dioxane dibromide mediated bromination of substituted coumarins under solvent-free conditions

• Subrata Kumar Chaudhuri,
• Sanchita Roy and
• Sanjay Bhar

Beilstein J. Org. Chem. 2012, 8, 323–329, doi:10.3762/bjoc.8.35

• /bjoc.8.35 Abstract An efficient solvent-free protocol for regioselective bromination of substituted coumarins has been developed by using dioxane dibromide as the solid brominating agent. The efficacy of the solvent-free protocol has been established. The effects of the electronic nature and location

• of the substituents on the outcome of the reaction have been rationalized with a proposed mechanism. Keywords: coumarins; solvent-free reaction; substituents; vinylic bromination; Introduction Brominated coumarins have immense synthetic, biological and industrial importance due to their occurance

• ], and for the selective synthesis of α-bromo and α,α-dibromoalkanones supported on silica gel under solvent-free conditions and microwave irradiation [13]. As a part of our endeavor to develop novel solvent-free protocols for important organic transformations, we have reported the efficient synthesis of