37858-01-8Relevant articles and documents
Reaction Route and Mechanism of the Direct N-Alkylation of Sulfonamides on Acidic Mesoporous Zeolite β-Catalyst
Fu, Wenqian,Shen, Runsheng,Bai, Enhui,Zhang, Lei,Chen, Qun,Fang, Zhongxue,Li, Guangchao,Yi, Xianfeng,Zheng, Anmin,Tang, Tiandi
, p. 9043 - 9055 (2018/09/11)
Development of highly active heterogeneous catalysts with strong acidity and mesoporous structure is a highly attractive strategy for organic synthesis. In this study, a mesoporous zeolite beta (HBeta-M) with bulky particle size and strong acidity was synthesized and used in the direct N-alkylation of sulfonamides with alcohols. The strongly acidic HBeta-M had a higher intrinsic activity with initial turnover frequency of 11 × 10-2 s-1 than those of H-form mordenite nanosheets (3.3 × 10-2 s-1) and montmorillonite (4.0 × 10-2 s-1) catalysts. The experiment and characterization results demonstrate that there are two parallel reaction routes on the acidic catalysts. One route is the reaction of benzhydrol with p-toluenesulfonamide (route I). Another route is the reaction of dibenzhydryl ether, arising from route I, with p-toluenesulfonamide (route II), which is found in this work. The reaction rate of route I (13 × 10-3 mol kg-1 s-1) was higher than that of route II (9.8 × 10-3 mol kg-1 s-1) on HBeta-M, but route II predominantly contributed to the formation of the target product with high selectivity. Hereby, a complete reaction mechanism is proposed in this work.
Ambident reactivities of pyridone anions
Breugst, Martin,Mayr, Herbert
supporting information; experimental part, p. 15380 - 15389 (2010/12/24)
The kinetics of the reactions of the ambident 2- and 4-pyridone anions with benzhydrylium ions (diarylcarbenium ions) and structurally related Michael acceptors have been studied in DMSO, CH3CN, and water. No significant changes of the rate constants were found when the counterion was varied (Li+, K+, NBu4+) or the solvent was changed from DMSO to CH3CN, whereas a large decrease of nucleophilicity was observed in aqueous solution. The second-order rate constants (log k2) correlated linearly with the electrophilicity parameters E of the electrophiles according to the correlation log k2 = s(N + E) (Angew. Chem., Int. Ed. Engl. 1994, 33, 938-957), allowing us to determine the nucleophilicity parameters N and s for the pyridone anions. The reactions of the 2- and 4-pyridone anions with stabilized amino-substituted benzhydrylium ions and Michael acceptors are reversible and yield the thermodynamically more stable N-substituted pyridones exclusively. In contrast, highly reactive benzhydrylium ions (4,4′-dimethylbenzhydrylium ion), which react with diffusion control, give mixtures arising from N- and O-attack with the 2-pyridone anion and only O-substituted products with the 4-pyridone anion. For some reactions, rate and equilibrium constants were determined in DMSO, which showed that the 2-pyridone anion is a 2-4 times stronger nucleophile, but a 100 times stronger Lewis base than the 4-pyridone anion. Quantum chemical calculations at MP2/6-311+G(2d,p) level of theory showed that N-attack is thermodynamically favored over O-attack, but the attack at oxygen is intrinsically favored. Marcus theory was employed to develop a consistent scheme which rationalizes the manifold of regioselectivities previously reported for the reactions of these anions with electrophiles. In particular, Kornblum's rationalization of the silver ion effect, one of the main pillars of the hard and soft acid/base concept of ambident reactivity, has been revised. Ag + does not reverse the regioselectivity of the attack at the 2-pyridone anion by increasing the positive charge of the electrophile but by blocking the nitrogen atom of the 2-pyridone anion.
Transformation of Carbinols by RuCl2(PPh3)3 and by Some Other Transition-Metal Catalysts
Pri-Bar, Ilan,Buchman, Ouri,Schumann, Hebert,Kroth, Heinz J.,Blum, Jochanan
, p. 4418 - 4428 (2007/10/02)
Several platinoid metal catalysts have been shown to promote reductive coupling, dehydration, disproportionation, and dehydrogenation of diarylcarbinols.Mechanistic studies were performed at 180-210 deg C with benzhydrol as substrate and RuCl2(PPh3)3 as catalyst.In aromatic hydrocarbon solvents the main process is reductive coupling.In this medium solvated RuCl2(PPh3)2 is suggested to be the active catalyst.In dimethyl sulfoxide the starting complex is transformed initially into RuCl2(PPh3)(Me2SO)2 and causes chiefly carbinol dehydrogenation.Ruthenium alkoxides are implied as common reaction intermediates in all four catalyses.Ruthenium hydrides are suggested to take part in the reductive coupling, disproportionation, and dehydrogenation processes.Some aliphatic and primary aromatic alcohols that do not react by themselves in the presence of RuCl2(PPh3)3 can both serve as active hydrogen donors and form crossover products in the presence of secondary and tertiary aromatic carbinols.
