Et₃B-mediated and palladium-catalyzed direct allylation of β-dicarbonyl compounds with Morita–Baylis–Hillman alcohols

• Ahlem Abidi,
• Yosra Oueslati and
• Farhat Rezgui

Beilstein J. Org. Chem. 2016, 12, 2402–2409, doi:10.3762/bjoc.12.234

• spectra (EI) were recorded on an Hewlett-Packard (70 eV) apparatus. Analytical thin-layer chromatography (TLC) was performed using Fluka Kieselgel 60 F254 precoated silica gel plates. Visualization was achieved by UV light (254 nm). Flash chromatography was performed using Merck silica gel 60 and a

The weight of flash chromatography: A tool to predict its mass intensity from thin-layer chromatography

• Freddy Pessel,
• Jacques Augé,
• Isabelle Billault and
• Marie-Christine Scherrmann

Beilstein J. Org. Chem. 2016, 12, 2351–2357, doi:10.3762/bjoc.12.228

• Purification by flash chromatography strongly impacts the greenness of a process. Unfortunately, due to the lack of the relevant literature data, very often this impact cannot be assessed thus preventing the comparison of the environmental factors affecting the syntheses. We developed a simple mathematical

• approach to evaluate the minimum mass intensity of flash chromatography from the retention factor values determined by thin-layer chromatography. Keywords: environmental factor; flash chromatography; green metrics; mass intensity; purification; Introduction As part of a more respectful environmental

• here a method to evaluate such an item. This tool can also allow the chemist to evaluate, from a thin-layer chromatography (TLC), the minimum mass required to perform a flash chromatography. Our calculations are based on the preparative chromatographic technique largely used by chemists [10][11][12

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

• the mixture was purified by flash chromatography for the structural characterization of the major product. As it is reported in Table 2 we obtained good to excellent yields of acetylated products for all the substrates belonging to NTC group. More than one reaction cycle was needed when the reactant

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

• described in the previous section. In all cases, the solid catalyst was eventually recovered by filtration and the reaction mixture was analysed by high resolution capillary GC with a fused silica capillary column SE52 (5% phenyl, 95% methyl polysiloxane, 30 m × 25 mm). The products were isolated by flash

• chromatography on silica gel (eluent = hexane/ethyl acetate) and characterised by multinuclear NMR. Anchoring methodologies: a) impregnation; b) covalent binding. Activity of the supported sulfonic acid catalyst within the first six cycles. Reaction conditions: 1 mol % cat., acid:alcohol ratio = 1:1, solvent

Economical and scalable synthesis of 6-amino-2-cyanobenzothiazole

• Jacob R. Hauser,
• Hester A. Beard,
• Mary E. Bayana,
• Katherine E. Jolley,
• Stuart L. Warriner and
• Robin S. Bon

Beilstein J. Org. Chem. 2016, 12, 2019–2025, doi:10.3762/bjoc.12.189

• flash chromatography. No conversion of 6 to 13 was observed in the absence of DABCO, which demonstrates the essential role of DABCO as a cyanation catalyst under these conditions. In addition, when the more electron rich 6-amino-2-chlorobenzothiazole (7) was subjected to the DABCO-catalysed cyanation

Synthesis and characterization of fluorinated azadipyrromethene complexes as acceptors for organic photovoltaics

• Forrest S. Etheridge,
• Roshan J. Fernando,
• Sandra Pejić,
• Matthias Zeller and
• Geneviève Sauvé

Beilstein J. Org. Chem. 2016, 12, 1925–1938, doi:10.3762/bjoc.12.182

• by rotary evaporation of dichloromethane, and purified by flash chromatography using a dichloromethane/hexane mixture as the eluent (starting with 80% hexane and gradually decreasing the amount to 60%). The final pure product was obtained as a dark blue solid after removal of solvents (0.091 g, 87

• 60 °C. The solution turned bright blue. After 16 h of heating, anhydrous ZnCl2 (0.023 g, 0.168 mmol) was added and heating was continued for another 16 h. The crude product was obtained by rotary evaporation of dichloromethane and purified by flash chromatography using a dichloromethane/hexane

• obtained by rotary evaporation of dichloromethane and purified by flash chromatography using a dichloromethane/hexane mixture as the eluent (starting with 80% hexane and gradually decreasing to 60%). The final pure product was obtained as a dark blue solid after removal of solvents (0.119 g, 69%). 1H NMR

Experimental and theoretical insights in the alkene–arene intramolecular π-stacking interaction

• Valeria Corne,
• Ariel M. Sarotti,
• Carmen Ramirez de Arellano,
• Rolando A. Spanevello and
• Alejandra G. Suárez

Beilstein J. Org. Chem. 2016, 12, 1616–1623, doi:10.3762/bjoc.12.158

• 40:60. The diastereomeric mixture of 4 and 5 was easily separated by flash chromatography. Finally, acrylates 6a,b were prepared by reaction of the corresponding alcohol 5 with acryloyl chloride in the presence of Et3N at 0 °C. The corresponding acrylic ester could not be obtained from the epimeric

Catalytic Chan–Lam coupling using a ‘tube-in-tube’ reactor to deliver molecular oxygen as an oxidant

• Carl J. Mallia,
• Paul M. Burton,
• Alexander M. R. Smith,
• Gary C. Walter and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2016, 12, 1598–1607, doi:10.3762/bjoc.12.156

• excess copper present and the organic solvent from eluent evaporated under reduced pressure. The resultant crude material was then purified using flash chromatography. General flow scheme for catalytic Chan–Lam reaction. Observed trend for the effect of changing oxygen pressure on the NMR yield of 19

Enantioselective addition of diphenyl phosphonate to ketimines derived from isatins catalyzed by binaphthyl-modified organocatalysts

• Hee Seung Jang,
• Yubin Kim and
• Dae Young Kim

Beilstein J. Org. Chem. 2016, 12, 1551–1556, doi:10.3762/bjoc.12.149

• °C. The reaction mixture was stirred for 12–48 h. After completion of the reaction, the resulting solution was concentrated in vacuo and the obtained residue was purified by flash chromatography (EtOAc–hexane) to afford the corresponding adducts 3. Structure of chiral bifunctional organocatalysts

Beta-hydroxyphosphonate ribonucleoside analogues derived from 4-substituted-1,2,3-triazoles as IMP/GMP mimics: synthesis and biological evaluation

• Tai Nguyen Van,
• Audrey Hospital,
• Corinne Lionne,
• Lars P. Jordheim,
• Charles Dumontet,
• Christian Périgaud,
• Laurent Chaloin and
• Suzanne Peyrottes

Beilstein J. Org. Chem. 2016, 12, 1476–1486, doi:10.3762/bjoc.12.144

• water and extracted with EtOAc, the organic layers were combined and dried over with MgSO4 and concentrated under reduced pressure. The crude material was purified by flash chromatography (CH2Cl2/EtOAc) to give the desired product. General procedure D for removal of sugar protecting groups: The

• protected derivative was dissolved in methanolic ammonia (20 mL/mmol) at room temperature and stirred overnight, and then the reaction mixture was concentrated under vacuum. The crude material was purified by flash chromatography (CH2Cl2/MeOH) to give the desired product. General procedure E for diethyl

Synthesis of ferrocenyl-substituted 1,3-dithiolanes via [3 + 2]-cycloadditions of ferrocenyl hetaryl thioketones with thiocarbonyl S-methanides

• Grzegorz Mlostoń,
• Róża Hamera-Fałdyga,
• Anthony Linden and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2016, 12, 1421–1427, doi:10.3762/bjoc.12.136

• spectrometer. The 1H and 13C NMR spectra were measured on a Bruker Avance III (600 and 150 MHz, respectively) instrument in CDCl3, using the solvent signal as reference. ESIMS were recorded on a Varian 500-MS IT Mass Spectrometer. The elemental analyses were performed on a Vario Micro Cube apparatus. Flash

• chromatography was carried out using Silica gel 60 (Sigma-Aldrich, 230–400 mesh). The notation Fc in this study represents ferrocenyl. Applied reagents such as ferrocenyl-substituted thioketones (1) [1], thiobenzophenone (4a) [18], and thiofluorenone (4b) [19] were prepared using known procedures. 1,1,3,3

Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(−)-myrtenol nitrate

• Sean P. Bew,
• Glyn D. Hiatt-Gipson,
• Graham P. Mills and
• Claire E. Reeves

Beilstein J. Org. Chem. 2016, 12, 1081–1095, doi:10.3762/bjoc.12.103

• dihydroxylation [24] afforded the inseparable (flash chromatography) (±)-3-methylbut-3-ene-1,2-diol (rac-17) and (±)-2-methylbut-3-ene-1,2-diol (rac-18) in a 3:2 ratio and unoptimized 67% yield (Scheme 3). Investigating O-nitrate ester formation the rac-17/rac-18 mixture was dissolved in dichloromethane

• times at −78 °C afforded low yields of complex mixtures that proved, essentially, inseparable by flash chromatography. Upon closer inspection of the Olah report we were intrigued by the fact that of the eleven alcohols employed none of the corresponding O-nitrate esters, i.e., 23–33 (Scheme 4) contained

Separation and identification of indene–C₇₀ bisadduct isomers

• Bolong Zhang,
• Jegadesan Subbiah,
• David J. Jones and
• Wallace W. H. Wong

Beilstein J. Org. Chem. 2016, 12, 903–911, doi:10.3762/bjoc.12.88

• device performance. In a previous communication [9], an isomer of IC70BA was obtained by chromatographic separation using both flash chromatography and high pressure liquid chromatography (HPLC). X-ray crystallography revealed that this sample contained the 2 o’clock-B isomer (Figure 2b). This material

• mixture of IC70BA was achieved by heating C70 with indene at 180 °C in 1,2-dichlorobenzene [9]. Following the reaction, flash chromatography (silica gel, toluene: cyclohexane, 1:9) was performed to remove any excess reagents, mono-adducts of C70 as well as other impurities. In our previous work, the

• mixture of IC70BA was separated into two fractions by means of flash chromatography; however in this case these two fractions were combined and further purified by HPLC using a Cosmosil Buckyprep-D column (4.6 i.d. × 250 mm, toluene, 0.2 mL/min, UV detection 325 nm). More than thirteen peaks were observed

Bi- and trinuclear copper(I) complexes of 1,2,3-triazole-tethered NHC ligands: synthesis, structure, and catalytic properties

• Shaojin Gu,
• Jiehao Du,
• Jingjing Huang,
• Huan Xia,
• Ling Yang,
• Weilin Xu and
• Chunxin Lu

Beilstein J. Org. Chem. 2016, 12, 863–873, doi:10.3762/bjoc.12.85

• was extracted with CH2Cl2. The organic layer was separated from the aqueous phase. After the organic phase was dried over MgSO4, the solution was filtered and concentrated under vacuum. The residue was purified by flash chromatography (silica gel, petroleum ether/ethyl acetate, 3:1) to give the

Supported bifunctional thioureas as recoverable and reusable catalysts for enantioselective nitro-Michael reactions

• José M. Andrés,
• Miriam Ceballos,
• Alicia Maestro,
• Isabel Sanz and
• Rafael Pedrosa

Beilstein J. Org. Chem. 2016, 12, 628–635, doi:10.3762/bjoc.12.61

• = triplet, q = quartet, m = multiplet, br = broad), coupling constants in Hertz, and integration. Flash chromatography was carried out using silica gel (230–240 mesh). TLC analysis was performed on glass-backed plates coated with silica gel 60 and an F254 indicator, and visualized by either UV irradiation

• finished (TLC). The catalyst was filtered off and washed with DCM (3 × 1 mL). The solvent was removed under reduced pressure, the crude mixture subjected to flash chromatography to afford the Michael adduct. The diastereomeric ratio was determined by 1H NMR spectroscopy of the purified product. The

• balls were washed with CH2Cl2, the catalyst was filtered off and washed with CH2Cl2 and methanol. The resulting solution was concentrated in vacuo, and the product was purified by flash chromatography. The diastereomeric ratio was determined by 1H NMR spectroscopy of the purified product. The

New synthetic strategies for xanthene-dye-appended cyclodextrins

• Milo Malanga,
• Andras Darcsi,
• Mihaly Balint,
• Gabor Benkovics,
• Tamas Sohajda and
• Szabolcs Beni

Beilstein J. Org. Chem. 2016, 12, 537–548, doi:10.3762/bjoc.12.53

• ). At this stage, the crude already has acceptable purity (>90% based on TLC), but flash chromatography with a CH3CN–H2O gradient elution permits the removal of the remaining CD-related byproducts and further increases the purity. After this additional purification step, the compound, Rho-β-CD, has been

• precipitation/filtration with acetone. Flash chromatography using a 10:5:1 (v/v/v) CH3CN/H2O/NH4OH (25%) ratio as eluent permits the removal of the unreacted NH2-CD-related impurities. At this stage the compound, Flu-β-CD, has been extensively characterized by spectroscopic techniques. UV–vis characterization

Application of 7-azaisatins in enantioselective Morita–Baylis–Hillman reaction

• Qing He,
• Gu Zhan,
• Wei Du and
• Ying-Chun Chen

Beilstein J. Org. Chem. 2016, 12, 309–313, doi:10.3762/bjoc.12.33

• MBH reaction product 3 was purified by flash chromatography on silica gel using petroleum ether/EtOAc 6:1–3:1 as the eluent. Bioactive 7-azaisatins and their derivatives. Further exploration with 7-azaisatin 1a and comparison with the previous work by Zhou [5]. Screening conditions of the

Cascade alkylarylation of substituted N-allylbenzamides for the construction of dihydroisoquinolin-1(2H)-ones and isoquinoline-1,3(2H,4H)-diones

• Ping Qian,
• Bingnan Du,
• Wei Jiao,
• Haibo Mei,
• Jianlin Han and
• Yi Pan

Beilstein J. Org. Chem. 2016, 12, 301–308, doi:10.3762/bjoc.12.32

• mixture was charged onto silica gel and purified by flash chromatography to furnish the corresponding products 5 and 7. Cascade 1,2-difunctionalization and cyclization to construct heterocycles. Cyclization of cyclohexane (2a) with substituted N-(2-methylallyl)benzamide (reaction conditions: 4 (0.2 mmol

Synthesis and nucleophilic aromatic substitution of 3-fluoro-5-nitro-1-(pentafluorosulfanyl)benzene

• Javier Ajenjo,
• Martin Greenhall,
• Camillo Zarantonello and
• Petr Beier

Beilstein J. Org. Chem. 2016, 12, 192–197, doi:10.3762/bjoc.12.21

• compound 2 from 3 and 4 by distillation or column chromatography was not successful. Therefore, for preparative experiments we decided to run the fluorination in MeCN to about 40% conversion and isolated 2 from unreacted 1 by flash chromatography (Scheme 3). Another method for the synthesis of 2 is the

Effective immobilisation of a metathesis catalyst bearing an ammonium-tagged NHC ligand on various solid supports

• Krzysztof Skowerski,
• Jacek Białecki,
• Stefan J. Czarnocki,
• Karolina Żukowska and
• Karol Grela

Beilstein J. Org. Chem. 2016, 12, 5–15, doi:10.3762/bjoc.12.2

• of heterogeneous olefin metathesis [19][20][21][22][23][24][52]. Encouraged by this initial success, we deposited 8 on several other widely available solid supports, commonly utilised in everyday laboratory and industrial practice. Those included silica gel (flash chromatography grade), neutral

New metathesis catalyst bearing chromanyl moieties at the N-heterocyclic carbene ligand

• Agnieszka Hryniewicka,
• Szymon Suchodolski,
• Agnieszka Wojtkielewicz,
• Jacek W. Morzycki and
• Stanisław Witkowski

Beilstein J. Org. Chem. 2015, 11, 2795–2804, doi:10.3762/bjoc.11.300

• were recorded on a Nicolet series II Magna-IR 550 FTIR spectrometer. Flash chromatography (FC) was performed on silica gel 230–400 mesh. Catalysts: 1, 2, 3 and the Hoveyda–Grubbs 1st generation complex were purchased from Apeiron Synthesis. 2,2,5,7,8-Pentamethylchromane (10) was prepared from 2,3,5

Pyridylidene ligand facilitates gold-catalyzed oxidative C–H arylation of heterocycles

• Kazuhiro Hata,
• Hideto Ito,
• Yasutomo Segawa and
• Kenichiro Itami

Beilstein J. Org. Chem. 2015, 11, 2737–2746, doi:10.3762/bjoc.11.295

• by flash chromatography on silica gel to afford the coupling product 3 (Table 2). Oxidation of AuCl(PyC): The oxidation of AuCl(PyC) was performed according to the literature [16]. PhICl2 (54.8 mg, 0.20 mmol) was added into a solution of AuCl(PyC) (128 mg, 0.20 mmol) in CH2Cl2 (2.0 mL) under N2

A novel and practical asymmetric synthesis of dapoxetine hydrochloride

• Yijun Zhu,
• Zhenren Liu,
• Hongyan Li,
• Deyong Ye and
• Weicheng Zhou

Beilstein J. Org. Chem. 2015, 11, 2641–2645, doi:10.3762/bjoc.11.283

• and concentrated. The residue was purified via flash chromatography with petrol ether/ethyl acetate (20:1) to give 4 as a pale yellow solid. Yield 32.3 g (78.3%); mp 49–51 °C; −10 (c 0.8, CDCl3); 1H NMR (400 MHz, CDCl3/TMS) δ 8.10 (d, J = 8 Hz, 1H), 7.79 (d, J = 8 Hz, 1H), 7.51–7.28 (m, 8H), 6.81 (d

• ). The aqueous layer was extracted with EtOAc (20 mL, twice). The organic phase was washed with water, brine, dried over Na2SO4 and concentrated. The residue was purified by flash chromatography to afford dapoxetine as a colorless oil. Yield 4.95 g (74.7%); chiral purity (HPLC): 99.63%; 1H NMR (400 MHz

Copper-catalyzed stereoselective conjugate addition of alkylboranes to alkynoates

• Takamichi Wakamatsu,
• Kazunori Nagao,
• Hirohisa Ohmiya and
• Masaya Sawamura

Beilstein J. Org. Chem. 2015, 11, 2444–2450, doi:10.3762/bjoc.11.265

• to the mixture. The mixture was filtered through a short plug of silica gel, which was then washed with diethyl ether. After the solvent was removed under reduced pressure, flash chromatography on silica gel (0–5% EtOAc/hexane) provided 4aa (69.4 mg, 0.248 mmol) in 99% yield with >99:1 syn/anti

Easy access to heterobimetallic complexes for medical imaging applications via microwave-enhanced cycloaddition

• Nicolas Desbois,
• Sandrine Pacquelet,
• Adrien Dubois,
• Clément Michelin and
• Claude P. Gros

Beilstein J. Org. Chem. 2015, 11, 2202–2208, doi:10.3762/bjoc.11.239

• obtained by precipitation from a concentrated methanolic solution by slow addition of diethyl ether. Compound 3 was reacted with Ga(NO3)3 to lead to 10b in 94% yield after flash chromatography. The IR spectrum of 10b exhibits the characteristic band of the carbonyl stretching vibration from 1722 cm−1 to

• first dissolved in trifluoroacetic acid (TFA) and stirred at room temperature overnight. A brown oil was obtained upon concentration. The residue was then purified by flash chromatography. Chelation of Cu2+ with propargyl NOTA 4 was performed in aqueous solution by Cu(ClO4)2·6H2O. Purification of Cu