An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• -picoline can be readily oxidised via another gas-phase protocol using a fixed-bed reactor charged with vanadium pentoxide on high surface titanium dioxide (5–50 wt % vanadium). A modification of the sequence utilises a dehydrative amminolysis (ammoxidation) to furnish the corresponding 3-cyanopyridine

• , which can then be subsequently hydrolysed to nicotinic acid. The catalyst systems most commonly used in this high temperature ammoxidation are based on vanadium, molybdenum or antimony oxides supported on silica or alumina. Since the initial Chichibabin type sequence (step 1; Scheme 3) leading to 3

Camera-enabled techniques for organic synthesis

• Steven V. Ley,
• Richard J. Ingham,
• Matthew O’Brien and
• Duncan L. Browne

Beilstein J. Org. Chem. 2013, 9, 1051–1072, doi:10.3762/bjoc.9.118

• , such as the length of tubing used and the residence time required to effect a complete reaction. For subsequent work using oxygen gas, we moved to a more elegant but still simple tube-in-tube reactor setup [79]; in this case the oxidation of a lilac solution of vanadium(II) was used to indicate the

• of a sealed bottle (a) Sudan red dye is bleached by ozone gas permeating into solution through the reactor tubing, which visible (b) as a colour change from red to colourless. Similarly, solvation of oxygen gas (c) is followed by the oxidation of vanadium(III), which also has a distinct colour change

Thermodynamic and kinetic stabilization of divanadate in the monovanadate/divanadate equilibrium using a Zn-cyclene derivative: Towards a simple ATP synthase model

• Hanno Sell,
• Anika Gehl,
• Frank D. Sönnichsen and
• Rainer Herges

Beilstein J. Org. Chem. 2012, 8, 81–89, doi:10.3762/bjoc.8.8

• 0 to 7.5 mM in a system with a total concentration of vanadium [V]t of 1.5 mM at a pH value of 9.5, the ratio of vanadium bound in divanadate species rises from 5% to 23%, while the ratio of vanadium bound in monovanadate decreases from 95% to 77%. Hence, Zn-benzylcyclene 1 favors the condensation

• components leads to the mass balance equation system (3). The concentrations of the free components are the variables; the stability constants are the parameters to be optimized. In the 51V NMR titrations for the analysis of the vanadate/Zn-benzylcyclene system the total vanadium concentration [V]t at each

• system LAKE [23] for chemical equilibrium analysis and with MS-Excel [24]. Data of all titrations (78 titration points in total) were included in the calculation. The formation constants for the vanadium oxo-anions of the VO43−/H+-subsystem [21], the pKa value of Zn-benzylcyclene 1 [14] as well as 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

• that Lewis base catalysis made a much greater contribution to the overall catalytic activity of VO(salen)NCS in propylene carbonate than in dichloromethane. Keywords: cyanohydrin; Hammett; kinetics; propylene carbonate; vanadium; Introduction The last 15 years have witnessed an explosion of activity

• gives unprotected cyanohydrins which are prone to racemization. Pre-eminent amongst the synthetic catalysts are metal(salen) complexes, especially those based on titanium (1) and vanadium (2) [1] (Figure 1). Titanium complex 1 will catalyse the asymmetric addition of TMSCN to aromatic aldehydes with 80

• some ketones as substrates [22][23]. Recently, a modified version of complex 1, in which the two salen ligands are covalently linked together has been developed which allows the amount of catalyst used to be reduced to 0.0005 mol % [24][25]. Vanadium based catalysts such as 2 also catalyse the