Latent ruthenium–indenylidene catalysts bearing a N-heterocyclic carbene and a bidentate picolinate ligand

• Thibault E. Schmid,
• Florian Modicom,
• Adrien Dumas,
• Etienne Borré,
• Loic Toupet,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 1541–1546, doi:10.3762/bjoc.11.169

• a distorted square pyramidal geometry (Figure 1) [30]. The nitrogen atom of the picolinate occupied a position trans to the bulky NHC ligand, with the carboxylate group cis to the indenylidene. In order to determine the influence of the electronic parameters of the chelating pseudo-halide fragment

Pyridine-promoted dediazoniation of aryldiazonium tetrafluoroborates: Application to the synthesis of SF₅-substituted phenylboronic esters and iodobenzenes

• George Iakobson,
• Junyi Du,
• Alexandra M. Z. Slawin and
• Petr Beier

Beilstein J. Org. Chem. 2015, 11, 1494–1502, doi:10.3762/bjoc.11.162

• aryldiazonium tetrafluoroborates with NHC-Pd catalysts was reported recently [63]. When applied to 3a and 3b using Pd(OAc)2 and NHC ligand precursors L, the borylated products 2a and 2b were isolated in only moderate yields (Table 2, entries 1 and 2). However, it was found that the Pd catalyst was not required

Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition

• Regina Berg and
• Bernd F. Straub

Beilstein J. Org. Chem. 2013, 9, 2715–2750, doi:10.3762/bjoc.9.308

• strong σ-donor NHC ligand facilitates the formation of a copper(I) π-complex with significant π-backbonding, and thus activates the alkyne for the cycloaddition reaction. Based on DFT calculations, the mechanism displayed in Scheme 17 was proposed, which is in analogy to the catalytic cycle presented on

Synthesis, characterization and luminescence studies of gold(I)–NHC amide complexes

• Adrián Gómez-Suárez,
• David J. Nelson,
• David G. Thompson,
• David B. Cordes,
• Duncan Graham,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2013, 9, 2216–2223, doi:10.3762/bjoc.9.260

• metal center, with all C–Au–N angles in the range 173–179°. There was no evidence of any interactions between the gold center and the heteroatoms in complexes 3, 7, 8, 10 or 11. However, for 3, 7, 8, 10 and 11 there is an intermolecular contact between the aromatic nitrogen atom and the NHC ligand

• /SDD level of theory) [43] using Gaussian 09 [44]. The LUMO, HOMO and HOMO-1 are pictured in Figure 4. While the HOMO and HOMO-1 are centered predominantly on the amide ligand, the LUMO is localized on the aryl ring of the NHC ligand; we propose that the fluorescence behavior is due to a HOMO-to-LUMO

Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

• Kei Murakami and
• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 278–302, doi:10.3762/bjoc.9.34

• ). Recently, iron and cobalt have been regarded as efficient catalysts for carbometalation of simple alkynes. Shirakawa and Hayashi reported that iron salts could catalyze arylmagnesiation of arylacetylenes in the presence of an N-heterocyclic carbene (NHC) ligand (Scheme 29) [103]. In 2012, Shirakawa and

Alkyne hydroarylation with Au N-heterocyclic carbene catalysts

• Cristina Tubaro,
• Marco Baron,
• Andrea Biffis and
• Marino Basato

Beilstein J. Org. Chem. 2013, 9, 246–253, doi:10.3762/bjoc.9.29

• were recorded. However, whereas KAuBr4 was very quickly and completely deactivated, catalysts VI and VII retained their activity, highlighting the importance of the NHC ligand in stabilizing the catalytically active species. Catalyst VI (IPrAuCl) was particularly efficient and able to effect over 90

Extending the utility of [Pd(NHC)(cinnamyl)Cl] precatalysts: Direct arylation of heterocycles

• Anthony R. Martin,
• Anthony Chartoire,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2012, 8, 1637–1643, doi:10.3762/bjoc.8.187

• second precatalyst screening was performed. As shown in Table 3, better activity was observed for precatalysts 1 and 2, which have smaller ligands when compared to the NHCs in 3 and 4. This result suggests a strong dependence of the activity on the steric properties of the NHC ligand. Moreover, the small

• of the NHC ligand appears to play a major role in the catalytic efficiency, whereas the σ-donation properties (within the small electronic space examined) have little influence. Among the four complexes, [Pd(SIPr)(cin)Cl] exhibited the highest catalytic efficiency and was investigated for the

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• cyclophanic NHC ligand 60 and the related imidazopyridine-2-ylidene analog 59, generate gold complexes that behave in a divergent manner. While complex 59–AuCl, containing a poor π-acceptor ligand, is able to efficiently induce the (3 + 2) cycloaddition of eneallene 45 (R = Me, X = C(CO2Me)2, Ar = Ph, n = 1

• , Scheme 30), a related catalyst with the cyclophanic NHC ligand (60–AuCl) afforded the (2 + 2) cycloadduct with high selectivity and good yield (Scheme 31). From a mechanistic point of view, the authors suggested that both catalysts initially provide the common intermediate XXVI (Scheme 30). Then, a

Stereoselectivity of supported alkene metathesis catalysts: a goal and a tool to characterize active sites

• Christophe Copéret

Beilstein J. Org. Chem. 2011, 7, 13–21, doi:10.3762/bjoc.7.3

• coordinated to the metal centre) displayed selectivities at low conversions with (E/Z)0 significantly different from G-II catalysts (one NHC ligand): 2.7–3.2 vs 1.5–2.1, respectively (or 3.5–3.6 vs 2.0–2.7, if one looks at (E/Z)0 obtained by extrapolating (E/Z) ratio to 0 from values obtained under steady

New library of aminosulfonyl-tagged Hoveyda–Grubbs type complexes: Synthesis, kinetic studies and activity in olefin metathesis transformations

• Etienne Borré,
• Frederic Caijo,
• Christophe Crévisy and
• Marc Mauduit

Beilstein J. Org. Chem. 2010, 6, 1159–1166, doi:10.3762/bjoc.6.132

• weak influence on the behaviour of the catalysts in these cases. Finally, the reactivity profiles of 4a and 4g were compared in various metathesis reactions in order to evaluate the influence of the NHC ligand. The last point of our study was the comparison between catalysts in RCM of dienes or enynes

Backbone tuning in indenylidene–ruthenium complexes bearing an unsaturated N-heterocyclic carbene

• César A. Urbina-Blanco,
• Xavier Bantreil,
• Hervé Clavier,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2010, 6, 1120–1126, doi:10.3762/bjoc.6.128

• in this field [1][2][3][4][5][6][7][8]. Mixed complexes bearing both a phosphane and a NHC ligand, so-called 2nd generation catalysts, typically display better thermal stability and activities compared to 1st generation catalysts [9][10]. Key to the success and research activity involving 2nd

• improved stability, which is attributed to reduced initiation from poorer electron-donating ability of the NHC ligand. Conclusion The effects of modulating the nature of substituents on the backbone (C4 and C5) positions of the IMes ligand have permitted a quantification of the electronic and steric

Halide exchanged Hoveyda-type complexes in olefin metathesis

• Julia Wappel,
• César A. Urbina-Blanco,
• Mudassar Abbas,
• Jörg H. Albering,
• Robert Saf,
• Steven P. Nolan and
• Christian Slugovc

Beilstein J. Org. Chem. 2010, 6, 1091–1098, doi:10.3762/bjoc.6.125

• 16.10 ppm. All other features of the 1H NMR spectrum of 2 are similar to those of 1 indicating slightly hindered rotation of the N-heterocyclic carbene ligand and a trans-disposition of the two halide ligands. In contrast, the rotation of the NHC ligand around the Ru–NHC bond in 3 is hindered as shown

• occupied by C11 (of the NHC ligand) and the atom O1. The strong ruthenium–carbon bond to the carbene was found in the apical position of the square pyramidal coordination around the metal center. Selected bond lengths and angles are provided in Table 1. The overall geometry around the transition metal