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Search for "DBU" in Full Text gives 304 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

  • Pavel Nagorny and
  • Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

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  • with DBU and initiator (Ph2CHOH) to accomplish C=O activation and to promote the polymerization reactions (Scheme 6). Highly charged tetraalkylbisammonium salts (i.e., DABCO-Me2·2X) were found to be particularly active catalysts. Based on computational studies, the authors proposed that substrate
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Published 23 Dec 2016

Electron-transfer-initiated benzoin- and Stetter-like reactions in packed-bed reactors for process intensification

  • Anna Zaghi,
  • Daniele Ragno,
  • Graziano Di Carmine,
  • Carmela De Risi,
  • Olga Bortolini,
  • Pier Paolo Giovannini,
  • Giancarlo Fantin and
  • Alessandro Massi

Beilstein J. Org. Chem. 2016, 12, 2719–2730, doi:10.3762/bjoc.12.268

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  • 1a with 2-chlorobenzaldehyde 2a furnishing the benzoylated benzoin 3aa (double aroylation product) was selected as the benchmark (Table 1). Quite surprisingly, the polystyrene-supported 1,8-diazabicyclo [5.4.0]undec-7-ene 4 (PS-DBU) was completely inefficient (DMF, 35 °C, Ar atmosphere) in both
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Published 13 Dec 2016

Development of a continuous process for α-thio-β-chloroacrylamide synthesis with enhanced control of a cascade transformation

  • Olga C. Dennehy,
  • Valérie M. Y. Cacheux,
  • Benjamin J. Deadman,
  • Denis Lynch,
  • Stuart G. Collins,
  • Humphrey A. Moynihan and
  • Anita R. Maguire

Beilstein J. Org. Chem. 2016, 12, 2511–2522, doi:10.3762/bjoc.12.246

Graphical Abstract
  • . Elevating the temperature to 90 °C and employing DBU, as a more basic alternative to triethylamine, did not increase the reactivity. Hence, the focus was instead directed on converting the existing batch process (Scheme 2), with sodium ethoxide as base, into a stand-alone continuous process. Initially
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Published 24 Nov 2016

Sydnone C-4 heteroarylation with an indolizine ring via Chichibabin indolizine synthesis

  • Florin Albota,
  • Mino R. Caira,
  • Constantin Draghici,
  • Florea Dumitrascu and
  • Denisa E. Dumitrescu

Beilstein J. Org. Chem. 2016, 12, 2503–2510, doi:10.3762/bjoc.12.245

Graphical Abstract
  • followed by solvent extraction gave the sydnone-indolizines 9 in yields of over 50%. If the dissolution of the quaternary salts was incomplete, a small quantity of ethanol could be added. Alternatively, replacement of sodium bicarbonate with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and the use of
  • acetonitrile as solvent gave, in the case of the representative pyridinium bromide 8a, compound 9a in 53% yield. Similarly, 9a could be prepared in 54% yield by heating pyridine 6a under reflux with sydnone derivative 7 for four hours followed by the addition of DBU for cyclization. Although all three
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Published 23 Nov 2016

Inhibition of peptide aggregation by means of enzymatic phosphorylation

  • Kristin Folmert,
  • Malgorzata Broncel,
  • Hans v. Berlepsch,
  • Christopher H. Ullrich,
  • Mary-Ann Siegert and
  • Beate Koksch

Beilstein J. Org. Chem. 2016, 12, 2462–2470, doi:10.3762/bjoc.12.240

Graphical Abstract
  • ) with respect to the resin and two hour double couplings. A mixture of DBU (1,8-diazabicyclo[5,4,0]undec-7-ene) and piperidine (2% each) in DMF was used for Fmoc-deprotection (3 × 10 min). The resin was washed between each step with DMF and DCM (3 × 6 mL each). Peptides were cleaved from the resin by
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Published 18 Nov 2016

Useful access to enantiomerically pure protected inositols from carbohydrates: the aldohexos-5-uloses route

  • Felicia D’Andrea,
  • Giorgio Catelani,
  • Lorenzo Guazzelli and
  • Venerando Pistarà

Beilstein J. Org. Chem. 2016, 12, 2343–2350, doi:10.3762/bjoc.12.227

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  • condensation reactions were performed at room temperature by treating aldohexos-5-ulose derivatives with catalytic amounts of DBU (0.15 equiv) as an organic base promoting agent in toluene, a 1:1 mixture of toluene–CH2Cl2, or CH2Cl2 to circumvent solubility problems (Table 1, see Supporting Information File 1
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Published 08 Nov 2016

High performance p-type molecular electron donors for OPV applications via alkylthiophene catenation chromophore extension

  • Paul B. Geraghty,
  • Calvin Lee,
  • Jegadesan Subbiah,
  • Wallace W. H. Wong,
  • James L. Banal,
  • Mohammed A. Jameel,
  • Trevor A. Smith and
  • David J. Jones

Beilstein J. Org. Chem. 2016, 12, 2298–2314, doi:10.3762/bjoc.12.223

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  • 11b, cat. Pd2dba3·4t-Bu3P[HBF4], THF, K3PO4 (2M), 80 °C, 16 h, and ii) N-hexylrhodanine (10 equiv), CHCl3, cat DBU. Extracted UV–vis absorption peak positions for the BXxR series. (λmax in bold). Extracted fluorescence emission peak positions for the BXxR materials (λexcit 580 nm). Extracted UV–vis
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Published 02 Nov 2016

Isosorbide and dimethyl carbonate: a green match

  • Fabio Aricò and
  • Pietro Tundo

Beilstein J. Org. Chem. 2016, 12, 2256–2266, doi:10.3762/bjoc.12.218

Graphical Abstract
  • , several alternative catalysts and bases have been taken into consideration. Recently it has been reported that 1,5-diazabiciclo(5.4.0)undec-5-ene (DBU) can be used in stoichiometric amounts for the efficient synthesis of isosorbide via DMC chemistry (entry 4, Table 2) [66]. Under these reaction conditions
  • , isosorbide was obtained in pure form by filtration on a silica pad and evaporation of the DMC. Even when the amount of DBU was reduced to 5 mol % (entries 4–6, Table 2) the cyclic sugar was still formed in quantitative yield. It is also noteworthy that, although the catalyst employed is homogenous, the
  • amount of DBU used was, in the latter case (entry 6, Table 2) only 2.5 mol % for each tetrahydrofuranic cycle. The same synthetic approach can be also employed for the cyclisation of D-mannitol. The synthesis of isosorbide via DMC chemistry takes advantage of the enhanced reactivity of DMC in the
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Published 26 Oct 2016

The direct oxidative diene cyclization and related reactions in natural product synthesis

  • Juliane Adrian,
  • Leona J. Gross and
  • Christian B. W. Stark

Beilstein J. Org. Chem. 2016, 12, 2104–2123, doi:10.3762/bjoc.12.200

Graphical Abstract
  • Industrie (FCI). In addition, individual fellowships by the Ernst-Schering-Stiftung, the Dierks-von-Zweck-Stiftung and the Deutsche Bundesstiftung Umwelt (DBU) are gratefully acknowledged.
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Published 30 Sep 2016

p-Nitrophenyl carbonate promoted ring-opening reactions of DBU and DBN affording lactam carbamates

  • Madhuri Vangala and
  • Ganesh P Shinde

Beilstein J. Org. Chem. 2016, 12, 2086–2092, doi:10.3762/bjoc.12.197

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  • Madhuri Vangala Ganesh P Shinde Department of Chemistry, Indian Institute of Science Education and Research, Pune 411 008, India 10.3762/bjoc.12.197 Abstract The amidine bases DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) and DBN (1,5-diazabicyclo[4.3.0]non-5-ene) display nucleophilic behaviour
  • with a large substrate scope. Keywords: carbonates; DBN; DBU; lactams; p-nitrophenyl; Introduction Among various organic bases, amidines such as DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) and DBN (1,5-diazabicyclo[4.3.0]non-5-ene) having an imino group attached to the α-carbon of the amine are
  • synthetically useful and strong neutral bases. Besides, DBU and DBN catalyze various organic reactions such as dehydrohalogenations [1], carbonylations [2], amidations [3] and Baylis–Hillman reactions [4]. These bicyclic amidines have been thought to be non-nucleophilic bases, but meanwhile numerous examples
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Published 26 Sep 2016

Scope and limitations of a DMF bio-alternative within Sonogashira cross-coupling and Cacchi-type annulation

  • Kirsty L. Wilson,
  • Alan R. Kennedy,
  • Jane Murray,
  • Ben Greatrex,
  • Craig Jamieson and
  • Allan J. B. Watson

Beilstein J. Org. Chem. 2016, 12, 2005–2011, doi:10.3762/bjoc.12.187

Graphical Abstract
  • . Organic bases such as pyridine (Table 2, entry 2), DIPEA (Table 2, entry 4), and Et3N (Table 2, entry 6) were tolerated at 25 °C with DIPEA and Et3N also tolerated at 50 °C. DBU, however, was not tolerated at any temperature (Table 2, entry 8). With the exception of KOAc (Table 2, entry 1), all inorganic
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Published 08 Sep 2016

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

Graphical Abstract
  • therefore operate (Scheme 11) [63]. Munshi et al. also recently investigated the reaction of glycerol and DMC by proposing a novel ionic liquid catalyst based on the reaction of diazabicyclo[5.4.0]undec-7-ene (DBU) with an alcohol ROH and CO2 (Scheme 12) [64]. As best found reaction conditions (only 0.22
  • carbonyl moiety (Scheme 14). It must be noted that in these two examples the selectivity of the reaction could be tuned just by changing the catalyst precursor: by switching from the DBU-based IL to the DABCO–DMC IL, the selectivity changed from 82% for glycerol carbonate, to 83% for glycidol. In another
  • such systems was found to be higher than that of strong bases including DBU or DABCO. This phenomenon was observed by several authors [64][76] and explained by a cooperative ambiphilic (nucleophilic–electrophilic) activation effect in which the IL anion and cation may activate respectively the
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Published 26 Aug 2016

Rearrangements of organic peroxides and related processes

  • Ivan A. Yaremenko,
  • Vera A. Vil’,
  • Dmitry V. Demchuk and
  • Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

Graphical Abstract
  • of 2-alkenylcyclopentanones 276 and cyclopentenones 277 [358]. Thus, the treatment of a solution of endoperoxides 275 in CH2Cl2 with triethylamine while increasing the temperature from 0 °C to room temperature affords hydroxyketone 276. The use of the stronger base DBU results in the formation of 2
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Published 03 Aug 2016

On the cause of low thermal stability of ethyl halodiazoacetates

  • Magnus Mortén,
  • Martin Hennum and
  • Tore Bonge-Hansen

Beilstein J. Org. Chem. 2016, 12, 1590–1597, doi:10.3762/bjoc.12.155

Graphical Abstract
  • added DBU (1.4 mmol) and stirring was continued at 0 °C for 5 min before the N-halosuccinimide (1.1 mmol, NBS or NCS or NIS) of choice was added. There was an immediate color change from yellow to orange or red, and the conversion of EDA was completed in less than 5 min as judged by TLC analysis. After
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Published 26 Jul 2016

Flow carbonylation of sterically hindered ortho-substituted iodoarenes

  • Carl J. Mallia,
  • Gary C. Walter and
  • Ian R. Baxendale

Beilstein J. Org. Chem. 2016, 12, 1503–1511, doi:10.3762/bjoc.12.147

Graphical Abstract
  • , did not significantly change the isolated yield of 5. However, changing to the stronger base DBU (pKa in water at 25 °C = 13.5) [40] dramatically reduced the isolated yield (Table 1, entry 8). A wider temperature range was also investigated (Table 1, entries 9–11). This resulted in only a small
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Published 19 Jul 2016

Synthesis of 2-oxindoles via 'transition-metal-free' intramolecular dehydrogenative coupling (IDC) of sp2 C–H and sp3 C–H bonds

  • Nivesh Kumar,
  • Santanu Ghosh,
  • Subhajit Bhunia and
  • Alakesh Bisai

Beilstein J. Org. Chem. 2016, 12, 1153–1169, doi:10.3762/bjoc.12.111

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  • 4). These reactions were always associated with unreacted starting material (28–51%) and decomposition of the rest of the mass balance. Interestingly, when the base was changed to DBU (using 1.5 equiv DBU and 1.2 equiv of iodine) the desired 2-oxindole was isolated in 82% (conditions C). With this
  • result in hand, we thought of exploring IDC using C-alkylated substrates 10. For this purpose, a variety of C-alkylated β-N-arylamidoallyl, methallyl, dimethylallyl, and geranyl esters 10 were synthesized in good yields as per Figure 4. These substrates were then utilized in IDC-promoted by DBU/I2 and
  • of ‘transition-metal-free’ IDC using KOt-Bu/I2. Reproduced from [46]. C-Alkylation of anilides using KOt-Bu. Substrates scope of ‘transition-metal-free’ IDC of C-alkylated anilides using DBU/I2. Synthesis of 2-oxindoles via oxidative processes. Oxidative coupling of C-arylated anilides (±)-11a–d. The
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Published 08 Jun 2016

Modular synthesis of the pyrimidine core of the manzacidins by divergent Tsuji–Trost coupling

  • Sebastian Bretzke,
  • Stephan Scheeff,
  • Felicitas Vollmeyer,
  • Friederike Eberhagen,
  • Frank Rominger and
  • Dirk Menche

Beilstein J. Org. Chem. 2016, 12, 1111–1121, doi:10.3762/bjoc.12.107

Graphical Abstract
  • motif into 18, tosylisocyanate in combination with strong bases was required to achieve useful degrees of conversion towards the desired precursor 19. The best results were obtained with BuLi, as previously communicated [31], while weaker bases (NEt3, LHMDS, DBU, proton sponge) and less electron
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Published 02 Jun 2016

Muraymycin nucleoside-peptide antibiotics: uridine-derived natural products as lead structures for the development of novel antibacterial agents

  • Daniel Wiegmann,
  • Stefan Koppermann,
  • Marius Wirth,
  • Giuliana Niro,
  • Kristin Leyerer and
  • Christian Ducho

Beilstein J. Org. Chem. 2016, 12, 769–795, doi:10.3762/bjoc.12.77

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  • a first key step of the synthesis led to a 1:1 mixture of the two epimers 36 and 37, and the undesired lactone 37 could be epimerised and converted into 36 by treatment with DBU [98]. Epimerisation and simultaneous lactone opening could be achieved in another key step using L-valine tert-butyl ester
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Published 22 Apr 2016

Stereoselective amine-thiourea-catalysed sulfa-Michael/nitroaldol cascade approach to 3,4,5-substituted tetrahydrothiophenes bearing a quaternary stereocenter

  • Sara Meninno,
  • Chiara Volpe,
  • Giorgio Della Sala,
  • Amedeo Capobianco and
  • Alessandra Lattanzi

Beilstein J. Org. Chem. 2016, 12, 643–647, doi:10.3762/bjoc.12.63

Graphical Abstract
  • diastereoisomer of the racemic tetrahydrothiophenes, present at the equilibrium, was preferentially acylated by the enzyme to give the product in high ee. Different amines such as Et3N, DBU, TMG catalyze the sulfa-Michael/nitroaldol process of either trans-β-methyl-β-nitrostyrenes [21] and trans-β-nitrostyrenes
  • diastereoisomeric tetrahydrothiophenes were observed when using tertiary amines such Et3N, DBU or TMG [21][22]. At the outset, the sulfa-Michael/nitroaldol reaction was studied by reacting trans-β-nitrostyrene, (E)-1-phenyl-2-nitropropene and (E)-1-phenyl-2-nitrobutene in toluene at room temperature with 1,4
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Published 05 Apr 2016

The aminoindanol core as a key scaffold in bifunctional organocatalysts

  • Isaac G. Sonsona,
  • Eugenia Marqués-López and
  • Raquel P. Herrera

Beilstein J. Org. Chem. 2016, 12, 505–523, doi:10.3762/bjoc.12.50

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  • the acyl phosphonate 24a, in dichloromethane at room temperature, with subsequent addition of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and methanol to give the corresponding ester derivative 25a (Scheme 10a) [39]. The use of the analog squaramide 23 afforded the product with slightly lower selectivity
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Published 14 Mar 2016

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

  • Rajeev S. Menon,
  • Akkattu T. Biju and
  • Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

Graphical Abstract
  • reaction conditions. An intramolecular cross-benzoin condensation between aldehyde and ketone moieties was developed by Suzuki in 2003. The isoxazole-fused cyclohexanone 51 endowed with an aryl aldehyde underwent a smooth cross-benzoin cyclisation in the presence of the thiazolium catalyst 19 and DBU
  • precatalyst 54 and DBU promoted enantioselective intramolecular cross-benzoin reaction of 55 to afford chromanone 56 in excellent yield and enantioselectivity (Scheme 34). The NHC-precatalyst is conveniently prepared from camphor in 5 steps [51]. NHC generated from the N-tert-butyl-substituted imidazolium
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Published 09 Mar 2016

A quadruple cascade protocol for the one-pot synthesis of fully-substituted hexahydroisoindolinones from simple substrates

  • Hong-Bo Zhang,
  • Yong-Chun Luo,
  • Xiu-Qin Hu,
  • Yong-Min Liang and
  • Peng-Fei Xu

Beilstein J. Org. Chem. 2016, 12, 253–259, doi:10.3762/bjoc.12.27

Graphical Abstract
  • rac-3a in 59% yield (Table 1, entry 1). We then tested different catalysts to optimize the reaction. When Et3N was used, the reaction afforded the product with 41% yield (Table 1, entry 2). However, a complex mixture was observed when DBU was used (Table 1, entry 3), while no reaction was observed
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Published 11 Feb 2016

Versatile synthesis and biological evaluation of novel 3’-fluorinated purine nucleosides

  • Hang Ren,
  • Haoyun An,
  • Paul J. Hatala,
  • William C. Stevens Jr,
  • Jingchao Tao and
  • Baicheng He

Beilstein J. Org. Chem. 2015, 11, 2509–2520, doi:10.3762/bjoc.11.272

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  • moieties to investigate the impact of a 3’-fluorine atom on the biological activity of nucleosides. The 6-chloropurine was silylated with trimethylsilyl triflate and then glycosylated with the universal intermediate 3’-fluoro-3’-deoxy-β-D-ribofuranose 25 using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to
  • -substituted purine nucleoside derivatives (Scheme 5). The 2-amino-6-chloropurine (47) was glycosylated with the 3’-fluorine riboside 25 under DBU and trimethylsilyl triflate conditions. The corresponding protected intermediate nucleoside 48 was obtained in 78% yield and utilized for further derivatization
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Published 09 Dec 2015

Copper-catalyzed asymmetric conjugate addition of organometallic reagents to extended Michael acceptors

  • Thibault E. Schmid,
  • Sammy Drissi-Amraoui,
  • Christophe Crévisy,
  • Olivier Baslé and
  • Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 2418–2434, doi:10.3762/bjoc.11.263

Graphical Abstract
  • were reported. In order to fully demonstrate the synthetic significance of such a methodology, compounds 27 were reconjugated in the presence of DBU and subsequently reacted in the 1,4-ACA (Scheme 5). The optimized conditions for the conversion of 28 to 29 involved copper(I) thiophene-2-carboxylate
  • ,β,γ,δ-unsaturated thioesters produced from a Horner–Wadsworth–Emmons reagent were submitted to a 1,6-ACA catalyzed by the L8/CuBr·SMe2 system, followed by a reconjugation reaction in the presence of DBU to selectively afford 37 (ratio between 1,6 and 1,4-ACA products ranged from 85/15 to 99/1) in
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Published 03 Dec 2015

Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

  • Kevin Lafaye,
  • Cyril Bosset,
  • Lionel Nicolas,
  • Amandine Guérinot and
  • Janine Cossy

Beilstein J. Org. Chem. 2015, 11, 2223–2241, doi:10.3762/bjoc.11.241

Graphical Abstract
  • by focusing on amine-mediated degradation of GII and they highlighted various plausible decomposition pathways depending on the nature of the amine [45]. At first, the reaction between GII and various amines such as n-butylamine (a), pyrrolidine (b), morpholine (c) and DBU (d) were examined by 1H NMR
  • catalyst (Table 1, entries 2 and 3). Interestingly the sp2 amine DBU did not induce any decomposition of the methylidene intermediate (Table 1, entry 4). In all decomposition cases, the main identified product was the phosphonium CH3PCy3+Cl− that would result from a nucleophile attack of the free PCy3
  • DBU, fast decomposition of the catalyst was noticed and only the presence of free PCy3 could be observed. According to the previous experiments, DBU was not able to decompose the methylidene resting-state and, consequently, a deprotonation of the metallacyclobutane 15 was hypothesized (Scheme 6). The
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Published 18 Nov 2015
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