Robust bifunctional aluminium–salen catalysts for the preparation of cyclic carbonates from carbon dioxide and epoxides

• Yuri A. Rulev,
• Zalina Gugkaeva,
• Victor I. Maleev,
• Michael North and
• Yuri N. Belokon

Beilstein J. Org. Chem. 2015, 11, 1614–1623, doi:10.3762/bjoc.11.176

• ). 3-(tert-Butyl)-5-(dimethylamino)-2-hydroxybenzaldehyde (6) Prepared by a modified literature procedure [28]. Pd/C (10%, 100 mg) was added to a solution of 3-(tert-butyl)-2-hydroxy-5-nitrobenzaldehyde 5 (200 mg, 0.9 mmol) and 40% aqueous formaldehyde (4.5 mL) in ethanol (20 mL). The reaction mixture

• was stirred under 1 bar of hydrogen at room temperature for 24 hours. Then, the Pd/C was removed by filtration on celite, the volume of the filtrate was reduced by half under reduced pressure. Distilled water was added to the solution, resulting in formation of an orange precipitate (140 mg, 70

Qualitative evaluation of regioselectivity in the formation of di- and tri-6-O-tritylates of α-cyclodextrin

• Keisuke Yoshikiyo,
• Yoshihisa Matsui and
• Tatsuyuki Yamamoto

Beilstein J. Org. Chem. 2015, 11, 1530–1540, doi:10.3762/bjoc.11.168

• , and finally, the benzyl groups were removed by hydrogenation with Pd/C to form tri-6-O-mesitylenesulfonyl-α-CD. The retention time in UFLC and the 1H NMR spectrum of the obtained mesitylenesulfonylate coincided with those of authentic 6A,6B,6E-tri-6-O-mesitylenesulfonyl-α-CD, respectively. Similar

• Industry Co., Ltd.), benzyl bromide and mesitylenesulfonyl chloride (Wako Pure Chemical Industries Ltd.) were used without further purification. Commercially available NaH in oil (50–77%) and Pd/C (Pd 10%) were used for the conversion of tri-6-O-trityl-α-CD to tri-6-O-mesitylenesulfonyl-α-CD. Reagent-grade

• dryness. The residue was chromatographed over silica gel, using hexane/ethyl acetate (2:1) as an eluent to give a fairly pure tri-6-O-mesitylenesulfonyl-per-O-benzyl-α-CD (0.51 g). The product was dissolved in 5 mL of acetic acid and hydrogenated in the presence of Pd/C (0.21 g) to remove the benzyl

Cross-metathesis reaction of α- and β-vinyl C-glycosides with alkenes

• Ivan Šnajdr,
• Kamil Parkan,
• Filip Hessler and
• Martin Kotora

Beilstein J. Org. Chem. 2015, 11, 1392–1397, doi:10.3762/bjoc.11.150

• -deoxyribosides on hand, the feasibility of catalytic hydrogenation was also briefly explored. Compounds possessing the heptenyl side chain (β-4b), tridecafluorononenyl side chain (β-4c), and the styryl side chain (β-4d) were chosen as substrates. In all cases the hydrogenation by using Pd/C under low pressure of

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• to a Glaser–Eglinton coupling to generate the macrocyclic bisacetylene derivative 52 in 94% yield. Finally, diyne 52 was subjected to a hydrogenation sequence with 10% Pd/C under 1 atm pressure of H2 to generate cyclophane derivative 53 (92%). Alternatively, cyclophane 53 was also obtained by

• dimeric cyclophane 242 (20%, Scheme 39) [174]. The reduction of the sulfonyl group with Mg/ethanol in the presence of 1,2-dibromoethane aided by TMSCl afforded cyclophane derivative 244 (80%). Subsequently, the hydrogenation of the double bond with Pd/C under a H2 atmosphere gave normuscopyridine (223, 84

The chemical behavior of terminally tert-butylated polyolefins

• Dagmar Klein,
• Henning Hopf,
• Peter G. Jones,
• Ina Dix and
• Ralf Hänel

Beilstein J. Org. Chem. 2015, 11, 1246–1258, doi:10.3762/bjoc.11.139

• of the hydrocarbons 2. Results and Discussion Catalytic hydrogenation We started our studies on the reactive behavior of polyolefins 2 with one of the formally simplest alkene reactions: catalytic hydrogenation. When diene 3 was hydrogenated under relatively mild conditions (Pd/C, EtOH, room temp

• . Even under mild conditions (Pd/C, EtOH/hexane, room temp.) it is readily reduced (Scheme 3). After 5 minutes of hydrogenation, three products were detected: the 1,6-adduct 8, a diene (main product); the mono olefin 9; and the fully saturated hydrocarbon 10. When the reaction time was increased, the

Synthesis of icariin from kaempferol through regioselective methylation and para-Claisen–Cope rearrangement

• Qinggang Mei,
• Chun Wang,
• Zhigang Zhao,
• Weicheng Yuan and
• Guolin Zhang

Beilstein J. Org. Chem. 2015, 11, 1220–1225, doi:10.3762/bjoc.11.135

• resulting in 3 without affecting the double bond of the prenyl residue was another challenge. The hydrogenation of 10 with H2–Pd/C using EtOAc/MeOH (1:1) as solvent at 10 °C for 3 h, followed by column chromatography and recrystallization, provided 3 in 39% yield along with a large amount of the byproduct

• with reduced double bond. Then we tried a transfer hydrogenolysis method using ammonium formate/10% Pd/C [27], but the result was not improved. The desired product icaritin (3) was finally obtained in 84% yield from 10 when we used 1,4-cyclohexadiene/10% Pd/C in MeOH [28]. Hence, we optimized a

• ), reflux, 95%; (h) Pd/C, 1,4-cyclohexadiene, MeOH, 84%. Decomposition of 8. Claisen rearrangement of flavonol 8. Reagents and conditions: (a) 15, DMF/CHCl3, Ag2CO3, molecular sieves (4 Å, powder); (b) 16, CH2Cl2, Ag2O, molecular sieves (4 Å powder), 31% for 2 steps; (c) NH3 (g), MeOH, 94%; (d) NH3 (g

Hybrid macrocycle formation and spiro annulation on cis-syn-cis-tricyclo[6.3.0.0^2,6]undeca-3,11-dione and its congeners via ring-closing metathesis

• Sambasivarao Kotha,
• Ajay Kumar Chinnam and
• Rashid Ali

Beilstein J. Org. Chem. 2015, 11, 1123–1128, doi:10.3762/bjoc.11.126

• compound 11 (84%). Subsequently, the macrocyclic diindole derivative 11 was hydrogenated in the presence of H2/Pd/C to afford the saturated compound 6 (Scheme 3). To assemble the intricate spiro-polyquinane 7 via RCM as a key step [59][60][61][62], we started with the triquinane derivative 2. To this end

• , treatment of the hexacyclic dione 13 with Pd/C in EtOAc under hydrogen atmosphere (1 atm) gave the saturated spiro-polyquinane 7 in 90% yield (Scheme 4). Very few examples are known in the literature where multiple RCM was performed in a single operation to generate the molecules of medium molecular weight

• subjected to the hydrogenation protocol in the presence of H2/Pd/C to deliver the saturated bis-spiro-polyquinane derivatives 16a, 16b and 16a in an excellent yield (Table 1). Similarly, the dione 3a in the presence of an excess amount of NaH and allyl bromide gave the pentaallyl dione 14d in 67% yield

A new and convenient synthetic way to 2-substituted thieno[2,3-b]indoles

• Roman A. Irgashev,
• Arseny A. Karmatsky,
• Gennady L. Rusinov and
• Valery N. Charushin

Beilstein J. Org. Chem. 2015, 11, 1000–1007, doi:10.3762/bjoc.11.112

• adducts can be dehydrated easily by acidic agents to form crotonic condensation products, namely 3-(2-oxo-2-(hetero)arylethylidene)indolin-2-ones 10, which can undergo reduction of the C=C double bond in the presence of Na2S2O4 [29], H2/Pd(C) [30], or Me3P–H2O [31] (Scheme 2) into the corresponding

Mechanical stability of bivalent transition metal complexes analyzed by single-molecule force spectroscopy

• Manuel Gensler,
• Christian Eidamshaus,
• Maurice Taszarek,
• Hans-Ulrich Reissig and
• Jürgen P. Rabe

Beilstein J. Org. Chem. 2015, 11, 817–827, doi:10.3762/bjoc.11.91

• }butan-1-ol (4): A suspension of 4-{[2-(pyridin-3-yl)ethynyl]pyridin-5-yl}but-3-yn-1-ol (3) [27] (45 mg, 0.18 mmol) and Pd/C (45 mg, 100 wt %) in MeOH (3 mL) was stirred under an atmosphere of hydrogen (balloon) for 3 h until complete consumption of the starting material (by TLC). The mixture was

Novel stereocontrolled syntheses of tashiromine and epitashiromine

• Loránd Kiss,
• Enikő Forró and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2015, 11, 596–603, doi:10.3762/bjoc.11.66

• diluted with H2O (50 mL) and extracted with CH2Cl2 (3 × 20 mL). The organic layer was dried (Na2SO4) and concentrated under reduced pressure. The crude mixture was dissolved in EtOAc (30 mL), Pd/C (150 mg) was added and the mixture was stirred at 20 °C for 16 h. The catalyst was next filtered off through

Sequence-specific RNA cleavage by PNA conjugates of the metal-free artificial ribonuclease tris(2-aminobenzimidazole)

• Friederike Danneberg,
• Alice Ghidini,
• Plamena Dogandzhiyski,
• Elisabeth Kalden,
• Roger Strömberg and
• Michael W. Göbel

Beilstein J. Org. Chem. 2015, 11, 493–498, doi:10.3762/bjoc.11.55

• : 45 bar H2, Pd/C (10%), MeOH sat. with NH3, 60 °C, 5 h, rt, overnight, 37%; f: Mukaiyama’s reagent, NEt3, DMF, 22 h, rt, 56%. Boc-ON: 2-(tert-butoxycarbonyloxyimino)-2-phenylacetonitrile. Synthesis of PNA conjugates. Conditions: a: 1) 9, HOBt, DIC, DMF, rt, 24 h; 2) piperidine, DMF, rt, 30 min; b: 1

Selective methylation of kaempferol via benzylation and deacetylation of kaempferol acetates

• Qinggang Mei,
• Chun Wang,
• Weicheng Yuan and
• Guolin Zhang

Beilstein J. Org. Chem. 2015, 11, 288–293, doi:10.3762/bjoc.11.33

• equiv), K2CO3, acetone, rt, ii: NH3 (g), MeOH, 84%. Reagents and conditions: (a) BnBr (1.9 equiv), KI, K2CO3, acetone, 85%; (b) i: AlCl3, CH2Cl2, CH3CN, reflux, ii: 1 M HCl (aq), 86%; (c) Me2SO4 (1.3 equiv), K2CO3, acetone, rt, 85%; (d) NH3 (g), MeOH, 96%; (e) Pd/C, H2, 91%; (f) MeOH, acetone, 1 M HCl

• (aq), reflux, 82%; (g) Me2SO4 (3.3 equiv), K2CO3, acetone, 30 °C, 92%; (h) Pd/C, H2, 92%; (i) NH3 (g), MeOH, 94%; (j) Me2SO4 (1.5 equiv), K2CO3, acetone, MeOH, reflux, 82%; (k) Pd/C, H2, 93%. Reagents and conditions: (a) NH3 (g), MeOH, 95%; (b) Me2SO4 (2.6 equiv), K2CO3, acetone, rt, 87%; (c) Me2SO4

• (4.6 equiv), K2CO3, acetone, 30 °C, 95%; (d) Pd/C, H2, 91%; (e) Pd/C, H2, 89%. Direct methylation of kaempferol in acetone (yield, %). Supporting Information Supporting Information File 46: Experimental section; NMR and ESI-HRMS spectra of 1–23; NOESY spectra of 4 and 13; HMBC spectra of 4, 5, 7, 9

Synthesis of the furo[2,3-b]chromene ring system of hyperaspindols A and B

• Danielle L. Paterson and
• David Barker

Beilstein J. Org. Chem. 2015, 11, 265–270, doi:10.3762/bjoc.11.29

• representation of 7a. 3D representation of 7b. Possible mechanism for the formation of furo[2,3-b]chromenes 7a and 7b. Reagents and conditions: (i) triethylphosphonoacetate, DBU, THF, 48 h, 94%; (ii) H2, 10% Pd/C, EtOAc, 3 h, quant; (iii) BnBr, K2CO3, DMF, 3 h, 88%; (iv) LDA, THF, −78 °C, then allyl bromide, 24

• , 65 h, 80%; (vi) NaIO4, MeOH, H2O, 3 h, quant; (vii) 1-bromo-3,4-methylenedioxybenzene, t-BuLi, THF, −78 °C, 19 h, 87% 1:1 diastereoisomers; (viii) H2, 10% Pd/C, MeOH, 4 h, quant; (ix) 1:1 2 M HCl (aq):THF, 22 h, 7a 52%, 7b 32%. Supporting Information Supporting Information File 131: Experimental

Novel biphenyl-substituted 1,2,4-oxadiazole ferroelectric liquid crystals: synthesis and characterization

• Mahabaleshwara Subrao,
• Dakshina Murthy Potukuchi,
• Girish Sharada Ramachandra,
• Poornima Bhagavath,
• Sangeetha G. Bhat and
• Srinivasulu Maddasani

Beilstein J. Org. Chem. 2015, 11, 233–241, doi:10.3762/bjoc.11.26

• , (v) benzyl 2,2,2-trichloroacetimidate, CF3SO3H, n-hexane, rt, (vi) LiOH, MeOH, H2O, (vii) alkyl alcohol, DCC, DMAP, DCM, (viii) Pd/C, EtOAc, H2 (1 atm), (ix) 4-bromobenzoic acid, DCC, DMAP, DCM, (x) Pd(PPh3)2, Na2CO3, 1,2-DME, H2O, MW, 120 °C, 20 min. Phase transition temperatures (°C), enthalpy

Efficient deprotection of F-BODIPY derivatives: removal of BF₂ using Brønsted acids

• Mingfeng Yu,
• Joseph K.-H. Wong,
• Cyril Tang,
• Peter Turner,
• Matthew H. Todd and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 37–41, doi:10.3762/bjoc.11.6

• and conditions: (a) (i) 2,4-dimethyl-1H-pyrrole (5), TFA, DCM, rt, overnight; (ii) DDQ, rt, 2 h; (iii) Et3N, BF3·OEt2, rt, overnight, 27%; (b) NH2NH2·H2O, 10% Pd/C, EtOH, reflux, 2 h, 90%; (c) (i) 1 M HCl (aq), CH3OH, NaNO2, H2O, 0 °C, 1 h; (ii) NaN3, H2O, rt, 2 h, 71%; (d) propargyl-tri-Boc cyclam 12

Synthetic strategies for the fluorescent labeling of epichlorohydrin-branched cyclodextrin polymers

• Milo Malanga,
• Mihály Bálint,
• István Puskás,
• Kata Tuza,
• Tamás Sohajda,
• László Jicsinszky,
• Lajos Szente and
• Éva Fenyvesi

Beilstein J. Org. Chem. 2014, 10, 3007–3018, doi:10.3762/bjoc.10.319

• branched β-CD-polymer is a difficult task. 2) Reduction of the azido groups to amino moieties There are several and selective ways to perform the azido→amino conversion [22] and for compound 1 the hydrogenolytic method [23] based on hydrazine, catalyzed by Pd/C (Scheme 2) was selected. The reaction using

• hydrazine-Pd/C is fast and exhaustive (based on the evaluation of the IR spectra, Figure 3), but because of the laborious work-up (filtration, centrifugation, membrane filtration) and the partial inefficacy of the dialysis purification, this method needed further development. The overall progress of the

(2R,1'S,2'R)- and (2S,1'S,2'R)-3-[2-Mono(di,tri)fluoromethylcyclopropyl]alanines and their incorporation into hormaomycin analogues

• Armin de Meijere,
• Sergei I. Kozhushkov,
• Dmitrii S. Yufit,
• Christian Grosse,
• Marcel Kaiser and
• Vitaly A. Raev

Beilstein J. Org. Chem. 2014, 10, 2844–2857, doi:10.3762/bjoc.10.302

• -collidine, CH2Cl2, 4→20 °C, 14 h; v) FmocOSu, NaHCO3, acetone/water, 3 h; vi) H2, Pd/C, EtOAc, 20 °C, 2 h; vii) MeZOSu, NaHCO3, water/dioxane, 20 °C, 3 h; viii) All-Br, K2CO3, MeCN, 85 °C, 3 h, 60 °C, 16 h; ix) EDC, 4-pyrrolidinopyridine, CH2Cl2, 4→20 °C, 16 h; x) [Pd(PPh3)4], N-methylaniline, DME, 20 °C, 1

Synthesis of modified cyclic and acyclic dextrins and comparison of their complexation ability

• Kata Tuza,
• László Jicsinszky,
• Tamás Sohajda,
• István Puskás and
• Éva Fenyvesi

Beilstein J. Org. Chem. 2014, 10, 2836–2843, doi:10.3762/bjoc.10.301

• /0.27 g (~65%). HP-maltooligomers according to [17]: 1-O-Benzyl-HP G6, G7 and G8 -maltooligomers (0.15 mmol) were suspended in EtOH (3 mL), ammonium formiate (0.75 mmol) and 10% Pd/C (0.1 g) were added and the solutions were boiled for 30 min. Catalysts were filtered off and washed with water and the

Stereoselective synthesis of perillaldehyde-based chiral β-amino acid derivatives through conjugate addition of lithium amides

• Zsolt Szakonyi,
• Reijo Sillanpää and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2014, 10, 2738–2742, doi:10.3762/bjoc.10.289

• steps. The selective reduction of the isopropenyl double bond over a Pt/C catalyst resulted in 8A–D. The subsequent removal of the benzyl groups by hydrogenolysis over palladium on carbon (Pd/C) in a 1:1 mixture of n-hexane/EtOAc for 24 h gave primary amino esters 9A–D in excellent yields. The final

• , dry THF, −78 °C, 6 h, then NH4Cl (aq), overall yield: 87% (isomeric mixture), ratio 7A:7B:7C:7D = 76:17:6:1; (ii) 5% Pt/C, n-hexane/EtOAc 1:1, 1 atm. H2, rt, 16 h, yield: 90–92%; (iii) 5% Pd/C, n-hexane/EtOAc 1:1, 1 atm H2, rt, 24 h, yield: 92–95%; (iv) 10% HCl (aq), rt, 24 h, yield: 90–94%. Reagents

• , yield: 91%; (iii) 5% Pd/C, n-hexane/EtOAc 1:1, 1 atm H2, rt, 16 h, yield: 90%. Reagents and conditions: (i) 0.2 equiv KOt-Bu/t-BuOH, 40 °C, 24 h, yield: 93% (7D), 91% (13); (ii) 5% Pt/C, n-hexane/EtOAc 1:1, 1 atm H2, rt, 16 h, yield: 90% (8D), 91% (14); (iii) 5% Pd/C, n-hexane/EtOAc 1:1, 1 atm H2, rt

Formal total syntheses of classic natural product target molecules via palladium-catalyzed enantioselective alkylation

• Yiyang Liu,
• Marc Liniger,
• Ryan M. McFadden,
• Jenny L. Roizen,
• Jacquie Malette,
• Corey M. Reeves,
• Douglas C. Behenna,
• Masaki Seto,
• Jimin Kim,
• Justin T. Mohr,
• Scott C. Virgil and
• Brian M. Stoltz

Beilstein J. Org. Chem. 2014, 10, 2501–2512, doi:10.3762/bjoc.10.261

• was crossed with methyl vinyl ketone in 62% yield [34]. Reduction of enone 34 was achieved in the presence of Pd/C with H2 in EtOAc to furnish diketone 35 [34]. Chemoselective Wittig mono-olefination of 35 provided ω-enone (−)-32, spectroscopically identical to the material in Danishefsky’s racemic

A versatile δ-aminolevulinic acid (ΑLA)-cyclodextrin bimodal conjugate-prodrug for PDT applications with the help of intracellular chemistry

• Chrysie Aggelidou,
• Theodossis A. Theodossiou,
• Antonio Ricardo Gonçalves,
• Mariza Lampropoulou and
• Konstantina Yannakopoulou

Beilstein J. Org. Chem. 2014, 10, 2414–2420, doi:10.3762/bjoc.10.251

• conditions [(i) ΜeOH, Pd/C, H2, (ii) ΜeOH, formic acid, Pd/C, H2, (iii) ΜeOH, acetic acid, Pd/C, H2, (iv) ΜeOH, trifluoroacetic acid, Pd/C, H2]. A successful alternative was subsequently adopted comprising the linking of 4 to δ-azidolevulinic acid (8) (Scheme 2). The latter, having the nucleophilicity of the

• ), CF3COOH (250 μL) was added dropwise followed by addition of Pd/C (7.5 mg, 0.0071 mmol, 0.06 equiv). The mixture was hydrogenated with Η2 gas under stirring at rt for 48 h. Subsequently the catalyst was removed by repeated centrifugation cycles and the solution was evaporated to dryness, the residue re

• ) DCC, DMAP, DMF, 25–30 °C, 53%; vii) H2, Pd/C, 25–30 °C, 95%. Supporting Information Supporting Information File 580: Full experimental procedures and detailed analytical data for the synthesis of all precursor molecules of Scheme 1; additional NMR, IR and mass spectral data. Acknowledgements Funding

Synthesis and immunological evaluation of protein conjugates of Neisseria meningitidis X capsular polysaccharide fragments

• Laura Morelli,
• Damiano Cancogni,
• Marta Tontini,
• Alberto Nilo,
• Sara Filippini,
• Paolo Costantino,
• Maria Rosaria Romano,
• Francesco Berti,
• Roberto Adamo and
• Luigi Lay

Beilstein J. Org. Chem. 2014, 10, 2367–2376, doi:10.3762/bjoc.10.247

• ) NaOMe, MeOH; c) H2, Pd/C, MeOH/H2O, then H2O, Dowex 50W X8 resin (H+ form), then Dowex 50W X8 resin (Na+ form) (96% over two steps). Reagents and conditions: a) SIDEA, Et3N, DMSO: 11 (64%), 12 (49%), 13 (51%); b) CRM197, 100 mM NaPi pH 7.2. Characteristics of the synthesized glycoconjugates. rSBA titers

Derivatives of the triaminoguanidinium ion, 3. Multiple N-functionalization of the triaminoguanidinium ion with isocyanates and isothiocyanates

• Jan Szabo,
• Kerstin Karger,
• Nicolas Bucher and
• Gerhard Maas

Beilstein J. Org. Chem. 2014, 10, 2255–2262, doi:10.3762/bjoc.10.234

• ) N1···N7: N7–H 0.84 Å, N7···N1 2.584 Å, H···N1 2.12 Å, N7–H···N1 114.9°; b) N1···O1 (x, y+1, z): N1–H 0.85 Å, N1···O1 3.178 Å, H...O1 2.41 Å, N1–H···O1 150.8°. Conditions: a) benzaldehyde, ethanol/water, reflux, 1 h, 96% yield; b) H2, Pd/C (10%), MeOH, rt, 48 h, 78%; c) rac-Ph−CH(CH3)−CHO, water

N–O Cleavage reactions of heterobicycloalkene-fused 2-isoxazolines

• Jaipal R. Nagireddy,
• Geoffrey K. Tranmer,
• Emily Carlson and
• William Tam

Beilstein J. Org. Chem. 2014, 10, 2200–2205, doi:10.3762/bjoc.10.227

• observed a series of spots by TLC which were not separable by column chromatography. This prompted us to seek other reagents capable of inducing N–O cleavage. We subsequently attempted hydrogenation using Pd/C with various solvent systems (MeOH, MeOH/AcOH, AcOH/H2O) as well as hydrogen sources (H2

• moderate to excellent yields. We have investigated the efficacy of various cleavage conditions and found that although none of Mo(CO)6, Zn/AcOH, Fe/NH4Cl, Pd-C/H2, Pd(OH)2/H2 or Raney nickel/AcOH/H2 is suitable for cleavage of 2-isoxazolines fused to heterobicyclic frameworks, the combination of Raney

Synthesis of phosphoramidites of isoGNA, an isomer of glycerol nucleic acid

• Keunsoo Kim,
• Venkateshwarlu Punna,
• Phaneendrasai Karri and
• Ramanarayanan Krishnamurthy

Beilstein J. Org. Chem. 2014, 10, 2131–2138, doi:10.3762/bjoc.10.220

• failed under a variety of conditions (H2, 10% Pd/C, MeOH or EtOAc; Pd/C, DMF, cyclohexadiene; 10% Pd/C, NH4HCOO, acetone, reflux; 10% Pd-black, DMF, cyclohexadiene; (CH3)3SiI, CHCl3, 25 °C), for reasons that were not obvious to us. Consequently, we abandoned this approach and pursued a different