An aniline dication-like transition state in the Bamberger rearrangement

• Shinichi Yamabe,
• Guixiang Zeng,
• Wei Guan and
• Shigeyoshi Sakaki

Beilstein J. Org. Chem. 2013, 9, 1073–1082, doi:10.3762/bjoc.9.119

• water from Ar–N+H2OH is rate determining and a diprotonated species, Ar–N+H2OH2+, contributes significantly to the observed reaction rate at the acid-catalyst concentration [H2SO4] > 0.50 mol/L. The activation energy of the rearrangement in Scheme 1 was measured to be 24.8 kcal/mol. The SN1 mechanism

Peptoids and polyamines going sweet: Modular synthesis of glycosylated peptoids and polyamines using click chemistry

• Daniel Fürniss,
• Timo Mack,
• Frank Hahn,
• Sidonie B. L. Vollrath,
• Katarzyna Koroniak,
• Ute Schepers and
• Stefan Bräse

Beilstein J. Org. Chem. 2013, 9, 56–63, doi:10.3762/bjoc.9.7

• used 0.500 equiv of CuSO4·5H2O and 5.00 equiv sodium ascorbate as the catalytic system, which is a slightly higher catalyst concentration than reported for the reaction in solution [52]. To ensure, that the reaction proceeds completely we chose 2 days of agitation at ambient temperature and obtained

Organocatalytic asymmetric addition of malonates to unsaturated 1,4-diketones

• Sergei Žari,
• Tiiu Kailas,
• Marina Kudrjashova,
• Mario Öeren,
• Ivar Järving,
• Toomas Tamm,
• Margus Lopp and
• Tõnis Kanger

Beilstein J. Org. Chem. 2012, 8, 1452–1457, doi:10.3762/bjoc.8.165

• squaramide based catalysts VIII and IX are structurally similar, they have quite different properties. Catalyst IX is a self-association-free compound [21], while catalyst VIII forms associates, and the stereoselectivity of the reaction in its presence depends on the catalyst concentration [22]. The

Surfactant catalyzed convenient and greener synthesis of tetrahydrobenzo[a]xanthene-11-ones at ambient temperature

• Pravin V. Shinde,
• Amol H. Kategaonkar,
• Bapurao B. Shingate and
• Murlidhar S. Shingare

Beilstein J. Org. Chem. 2011, 7, 53–58, doi:10.3762/bjoc.7.9

• product yield slightly, accompanied by some impurities (Table 1, Entries 8–11). Catalyst concentration is a significant factor that exclusively affects the reaction rate and product yield. To study this, the reaction was performed at different concentrations of TTAB, i.e., 2.5, 5, 10, 15, and 20 mol

• %, and gave the product in 55%, 72%, 85%, 88% and 89% yield, respectively (Table 1, entry 7). Thus, it was clear that reaction rate increased with increasing catalyst concentration up to 15 mol % without any significant difference on further increasing the catalyst concentration. It means 15 mol % of

Tandem catalysis of ring-closing metathesis/atom transfer radical reactions with homobimetallic ruthenium–arene complexes

• Yannick Borguet,
• Xavier Sauvage,
• Guillermo Zaragoza,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2010, 6, 1167–1173, doi:10.3762/bjoc.6.133

• determine the nature of the catalytic species present in the reaction mixture after the metathesis step. No meaningful information could be obtained by 31P NMR spectroscopy even when acquisition was prolonged overnight to compensate for the low catalyst concentration in the sample. Visual inspection of the

Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate

• Michael North and
• Marta Omedes-Pujol

Beilstein J. Org. Chem. 2010, 6, 1043–1055, doi:10.3762/bjoc.6.119

• benzaldehyde at room temperature (entries 1 and 2) showed that increasing the reaction time increased the conversion without lowering the enantioselectivity. The conversion could also be increased by doubling the catalyst concentration (entry 3), though this did not enhance the enantioselectivity. Reducing the

• at each catalyst concentration were determined in triplicate, using two different batches of propylene carbonate, and the average value of the rate constant was calculated from all three data points for each concentration. As shown in Figure 3, plots of k2obs against the concentration of catalyst 2

From discovery to production: Scale- out of continuous flow meso reactors

• Peter Styring and
• Ana I. R. Parracho

Beilstein J. Org. Chem. 2009, 5, No. 29, doi:10.3762/bjoc.5.29

• ) based on 4-bromoanisole. However, the TOF was significantly reduced from the reaction carried out at half the flow rate (1.5 h−1). It should be noted that the TOFs in flow reactors are lower than in batch as we are dealing with small flows through a packed bed reactor and hence the catalyst

• concentration is necessarily high. If the rate limiting step in the reaction is the adsorption of the organobromide onto the surface of the catalyst, as we have proposed according to the Langmuir–Hinchelwood mechanism [17], then increasing the flow rate does not give sufficient time for adsorption of the aryl