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

• 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

• ][29] of its analogues (4c and 4j). Though the rate of reaction rate could be accelerated, the yield of 2-iminothiazolidin-4-one 4f was not good (41–66%) under both solution-phase and solvent-free conditions. Hence, as an attempt to optimize the yield, the solvent-free protocol was screened with and

• reaction is prominently enhanced under solvent-free conditions compared to that in the solution phase. Apparently, the intimacy of the highly polar reactants in the fused state in the absence of solvent may be responsible for the rate enhancement. Medicinally relevant 2-iminothiazolidin-4-ones. Retardation

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

• ]. Therefore, we support the use of BMIM-2-CO2 as a well-adapted alternative with respect to green polymerization approaches, (solvent-free conditions, no metal-based catalyst) as reported in this manuscript. However, the formation of higher molecular weight polymers with low polydispersities still remains to

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

• 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

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

• observed. The ball-milling approach was applied to the (S)-BINAM-L-prolinamide (II) catalysed direct aldol reaction between ketones and aldehydes under solvent-free conditions by Najera and co-workers (Scheme 3) [33][34]. Using 5–10 mol % of II and 10–20 mol % of benzoic acid as additive, the aldol

• solvent-free conditions by using a planetary ball mill (Scheme 7) [46]. Cinchona-derived chiral squaramide IX, at low catalyst loading of 0.5 mol %, efficiently catalyses the solvent-free Michael reaction of acetylacetone (9) with various substituted nitroalkenes 7 in a short reaction time (5–30 minutes

• -anhydride with alcohols catalysed by quinine (XII) was developed by Bolm’s group (Scheme 10) [58]. A variety of meso-anhydrides 18 were opened with a variety of alcohols 17 under solvent-free conditions to provide optically active dicarboxylic acid monoesters 19 in good to high yield (59–92%) and low to

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

• catalyst- and solvent-free conditions, we were surprised to find that the grinding mode could efficiently promote the reaction, and the corresponding Michael addition product 3a was obtained in nearly 100% yield. Therefore, we were encouraged to research the Michael addition systematically by the grinding

• method. Herein, we report a green protocol for the Michael addition of 1,3-dicarbonyl compounds to nitroalkenes under catalyst- and solvent-free conditions (Scheme 1). Utilizing this simple, rapid, low-cost and effective procedure, various nitro diketone derivatives were synthesized in high yields

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

• ) 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

• ], 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

• vicinal anti-dibromides through highly diastereoselective electrophilic addition of bromine across various electron-deficient and electron-rich double bonds [14] using DD under solvent-free conditions. Two compounds of the present investigation (2a and 2g in Table 1, see below) were synthesized during the

• detailed results are summarized in Table 1. When an unsubstituted coumarin (1a) was subjected to bromination with DD under solvent-free conditions, vicinally anti-dibromide 2a was obtained exclusively through electrophilic addition of bromine across the electron-deficient double bond of the conjugated δ

Continuous-flow hydration–condensation reaction: Synthesis of α,β-unsaturated ketones from alkynes and aldehydes by using a heterogeneous solid acid catalyst

• Magnus Rueping,
• Teerawut Bootwicha,
• Hannah Baars and
• Erli Sugiono

Beilstein J. Org. Chem. 2011, 7, 1680–1687, doi:10.3762/bjoc.7.198

• ). However, the best result was achieved when the reaction was conducted under solvent-free conditions (Table 1, entry 4). To probe the influence of microwave heating on this transformation, we examined the same transformation under batch conditions and without microwave irradiation. As shown in Table 1

Efficient and selective chemical transformations under flow conditions: The combination of supported catalysts and supercritical fluids

• M. Isabel Burguete,
• Eduardo García-Verdugo and
• Santiago V. Luis

Beilstein J. Org. Chem. 2011, 7, 1347–1359, doi:10.3762/bjoc.7.159

• very well suited to work under flow conditions [76][77]. Both catalysts were studied in flow conditions with scCO2 (40 °C, 8 MPa), with conventional solvents and under solvent-free conditions [74][78][79]. One of the main outcomes of the results obtained was the observation of a significant improvement

A straightforward approach towards combined α-amino and α-hydroxy acids based on Passerini reactions

• Ameer F. Zahoor,
• Sarah Thies and
• Uli Kazmaier

Beilstein J. Org. Chem. 2011, 7, 1299–1303, doi:10.3762/bjoc.7.151

• as well. The lower yield obtained in these cases probably results from stirring problems under these solvent-free conditions. To circumvent the problems caused by the α,β-unsaturated aldehyde, we hydrogenated 4 before oxidation to obtain the saturated aldehyde 7. And indeed, under our optimized

Novel synthesis of pseudopeptides bearing a difluoromethyl group by Ugi reaction and desulfanylation

• Jingjing Wu,
• Hui Li and
• Song Cao

Beilstein J. Org. Chem. 2011, 7, 1070–1074, doi:10.3762/bjoc.7.123

• , we tried to use it as one of the components in the preparations of the difluoromethylene-containing pseudopeptides by Ugi reaction. Indeed, the reaction of aniline, benzaldehyde, (isocyanomethyl)benzene with 2 proceeded efficiently under solvent-free conditions. Finally, we removed the protecting

• building block 2 were subjected to Ugi reaction under solvent-free conditions, followed by reductive cleavage of the phenylsulfanyl group. It was found that both Ugi reaction and desulfanylation proceeded smoothly for all substrates used to give the corresponding difluoromethylene-containing and

• methanol or under solvent-free conditions. Synthesis of 2,2-difluoro-2-(phenylthio)acetic acid (2). Synthesis of difluoromethylene-containing pseudopeptides (3a–m) and difluoromethyl-containing pseudopeptides (4a–m). Supporting Information Supporting Information File 310: Experimental procedures and

SbCl₃-catalyzed one-pot synthesis of 4,4′-diaminotriarylmethanes under solvent-free conditions: Synthesis, characterization, and DFT studies

• Ghasem Rezanejade Bardajee

Beilstein J. Org. Chem. 2011, 7, 135–144, doi:10.3762/bjoc.7.19

• and aprotic solvents such as dimethyl sulfoxide, N,N-dimethylformamide, dichloromethane, ethanol, diethyl ether, and n-hexane were examined: The best results were obtained under solvent-free conditions without microwave irradiation. The general route for the synthesis of these compounds is shown in

• Scheme 1. In a typical procedure, the reaction of benzaldehyde (0.50 mmol, 1 equiv) and N,N-dimethylaniline (1.25 mmol, 2.5 equiv) in the presence of SbCl3 (30 mol %) under solvent-free conditions at 120 °C for 4 h afforded compound 1a in 80% yield (Table 1, entry 1). To determine the influence of

• variety of aryl and heteroaryl aldehydes under solvent-free conditions to give substituted triarylmethanes. Using SbCl3 as catalyst, even electron-rich benzaldehydes such as 3,4,5-trimethoxybenzaldehyde gave the corresponding products in good yields. Operational simplicity, high yields, and the ability to

Synthesis of 3-(quinolin-2-yl)- and 3,6-bis(quinolin-2-yl)-9H-carbazoles

• Yang Li and
• Wentao Gao

Beilstein J. Org. Chem. 2010, 6, 966–972, doi:10.3762/bjoc.6.108

• )carbazoles under solvent-free conditions by the reaction of β-nitrovinylcarbazole or bis(β-nitrovinyl)carbazole with salicylaldehydes. In light of these findings, and in view of the prominent role structural diversity plays in medicinal and combinatorial chemistry, we felt that there was a real need for the

Synthesis of spiroannulated and 3-arylated 1,2,4-trioxanes from mesitylol and methyl 4-hydroxytiglate by photooxygenation and peroxyacetalization

• Axel G. Griesbeck,
• Lars-Oliver Höinck and
• Jörg M. Neudörfl

Beilstein J. Org. Chem. 2010, 6, No. 61, doi:10.3762/bjoc.6.61

• sensitization of triplet oxygen with meso-tetraphenylporphyrin (TPP) were performed in polystyrene beads under solvent-free conditions (Scheme 1) [18][19]. Numerous applications of the hydroperoxides 4 and 7, that result from the singlet oxygen ene reactions, have already been reported [20][21]. In context with

Zeolite catalyzed solvent- free one-pot synthesis of dihydropyrimidin- 2(1H)-ones – A practical synthesis of monastrol

• Mukund G. Kulkarni,
• Sanjay W. Chavhan,
• Mahadev P. Shinde,
• Dnyaneshwar D. Gaikwad,
• Ajit S. Borhade,
• Attrimuni P. Dhondge,
• Yunnus B. Shaikh,
• Vijay B. Ningdale,
• Mayur P. Desai and
• Deekshaputra R. Birhade

Beilstein J. Org. Chem. 2009, 5, No. 4, doi:10.3762/bjoc.5.4

• aliphatic aldehydes and thiourea were used low yields of DHPMs were realized. Results and Discussion We herein report a one-pot synthesis of DHPMs using a catalytic amount of zeolite under solvent-free conditions. In our quest to bring about the Biginelli reaction, we attempted the reaction using zeolite

• under solvent-free conditions. The well-known titanium silicate TS-1 (also known as titanium silicalite) [42] is a widely used heterogeneous catalyst. Therefore we decided to explore its suitability in the Biginelli reaction. For this purpose, a mixture of an aldehyde 1 (1 mmol), ethyl acetoacetate (2

Phase- vanishing halolactonization of neat substrates

• Nicole Windmon and
• Veljko Dragojlovic

Beilstein J. Org. Chem. 2008, 4, No. 29, doi:10.3762/bjoc.4.29

• reported along with the observation that it readily cyclizes to give the corresponding bromolactone [14][15]. For comparison, the reaction was done in dichloromethane and directly on neat reagents under solvent-free conditions (SFC) (caution: an extremely violent reaction!). In dichloromethane as a solvent

Transition- metal/Lewis acid free synthesis of acyl benzothiophenes via C-C bond forming reaction

• Sarbani Pal,
• Mohammad Ashrafuddin Khan,
• P. Bindu and
• P. K. Dubey

Beilstein J. Org. Chem. 2007, 3, No. 35, doi:10.1186/1860-5397-3-35

• under solvent-free conditions affording acyl benzothiophenes in good overall yields. Background Benzothiophene derivatives possessing an acyl group as one of the substituents on the five-membered ring are of immense medicinal value because of their promising pharmacological properties. For example

Synthesis of phosphorothioates using thiophosphate salts

• Babak Kaboudin and
• Fatemeh Farjadian

Beilstein J. Org. Chem. 2006, 2, No. 4, doi:10.1186/1860-5397-2-4

• alumina under solvent-free conditions using microwave irradiation. Introduction Organophosphorus compounds have found a wide range of application in the areas of industrial, agricultural, and medicinal chemistry owing to their biological and physical properties as well as their utility as synthetic

• acetate/sulfur/alumina under solvent-free conditions using microwave irradiation which produces high yields of phosphorothioates (Scheme 1). Results and Discussion Recently we have found that ammonium O,O'-diethyl thiophosphate can be obtained by reaction of diethylphosphite in the presence of a mixture

• of ammonium acetate/sulfur/acidic alumina under solvent-free conditions using microwave irradiation. [49] This reagent can be used as an efficient reagent for the conversion of epoxides to thiiranes. This ambident nucleophile has two potentially attacking atoms (S or O) and can attack with either of