3087-82-9Relevant academic research and scientific papers
Oxidant-free synthesis of benzimidazoles from alcohols and aromatic diamines catalysed by new Ru(II)-PNS(O) pincer complexes
Luo, Qi,Dai, Zengjin,Cong, Hengjiang,Li, Renjie,Peng, Tianyou,Zhang, Jing
, p. 15012 - 15022 (2017/11/14)
Benzimidazoles are chemically and pharmaceutically important, and an environmentally benign synthetic method based on acceptorless dehydrogenative condensation of primary alcohols and benzene-1,2-diamine is developed in this work. Three Ru(ii) hydride complexes [RuHCl(CO)(PNS(O))] (containing two isomers 1a and 1b) and [RuHCl(CO)(PPh3)(SNCNHC)]PF6 (2) based on two new quinoline-based ligands 2-(diphenylphosphanylmethyl)-8-phenylsulfinylquinoline (PNS(O)) and 1-mesityl-3-(8-phenylthioquinolyl-2-methyl)-2-imidazole carbene (SNCNHC) are prepared and fully characterized. These complexes catalyse the condensation of benzyl alcohol and benzene-1,2-diamine to 2-phenylbenzimidazole with the liberation of H2, and the catalytic activity follows the order: 1a ≈ 1b > 2. When 0.2 mol% of 1a and 2 mol% of NaBPh4 were used, various 2-functionalized benzimidazoles were obtained in good yields (70-85%) and high turnover numbers (TONs ～ 425). This homogeneous system does not need oxidants or stoichiometric strong bases (KOH or KOtBu, etc.) that are normally used in the reported homogeneous systems, and thus is a greener process.
Alkali metal salt solvation study in 1,1,3,3-tetramethylurea using nuclear magnetic resonance spectroscopy
Ciolino, Laura Ann,Barker, Barbara Jane
, p. 2206 - 2208 (2007/10/02)
The solution behavior of a series of alkali metal tetraphenylborates, perchlorates, and iodides in 1,1,3,3-tetramethylurea (TMU) has been studied by proton nuclear magnetic resonance (NMR) spectroscopy.TMU has a simple proton NMR spectrum consisting of one singlet at 2.75 ppm.Alkali metyl tetraphenylborates and perchloates were observed to be dissociated in TMU.Sodium iodide, however, was observed to be associated in TMU.Present results are compared with those from other NMR investigations in TMU and related nonaqueous solvents.Key words: alkali metal salt solvation, tetramethylurea; nuclear magnetic resonance, solute-solvent interactions
Ion Association. Comparison of Spectroscopic and Conductance Values of Association Constants
Gilkerson, William R.,Kendrick, Katherine L.
, p. 5352 - 5359 (2007/10/02)
Molar conductances of potassium, rubidium, and cesium picrate and of cesium tetraphenylborate have been determined in 2-butanone at 25 deg C over a concentration range of 0.1-1.6 mmol L-1.These Λ,C data together with those for lithium and sodium already determined in this laboratory were fitted by using the Lee-Wheaton (LW), the Pitts (P), the Fuoss 78 (F), and the Justice (J) conductance equations to obtain values of ion association constants, KA, and limiting molar conductances.Spectrophotometric absorbance changes were measured for sodium and cesium picrate and remeasured for lithium and tetra-n-butylammonium picrate at 380 nm and 25 deg C over a concentration range of 0.02-1.4 mmol L-1.Values of the cesium-133 NMR chemical shifts of cesium picrate were determined over a concentration range of 0.1-3 mmol L-1 while those for cesium tetraphenylborate were determined over a range from 0.25 to 10 mmol L-1.We calculated values of ion assiciation constants for the various salts using this spectroscopic data.The values of KA determined spectroscopically and the values determined conductimetrically are the same within experimental error with one exception; for cesium tetraphenylborate, the NMR value depends on the concentration range of data included in the analysis.
