640-61-9Relevant articles and documents
Micellar Effects in the Acid Denitrosation of N-Nitroso-N-methyl-p-toluenesulfonamide
Bravo, Carlos,Herves, Pablo,Leis, J. Ramon,Pena, M. Elena
, p. 8816 - 8820 (1990)
The acid denitrosation of N-methyl-N-nitroso-p-toluenesulfonamide (MNTS) has been studied in the presence of anionic, cationic, and nonionic surfactants.Both cationic and nonionic micelles inhibit the reaction through an effective association of the substrate to the micellar pseudophase.This bound substrate becomes unreactive due to the absence of protons in the micellar Stern layer.The kinetic results allow a quantitative estimation of the association constants.The reaction has also been studied in the presence of anionic surfactants, both functionalized and nonfunctionalized.With hydrogen dodecyl sulfate, the reaction is accelerated by the presence of surfactant and reaches a limiting value at high concentrations.The reaction with sodium dodecyl sulfate shows a familiar pattern of behavior, with the reactivity passing through a maximum as the concentration of surfactant is increased.These facts can be quantitatively understood in terms of the pseudophase ion-exchange model, assuming a constancy in the degree of micellar fraction charge neutralized.Numerical values for the rate constants in the micellar pseudophase could be obtained and compared with those in water.Association constants between MNTS and micellar aggregates can also be obtained as well as the equilibrium exchange constants between Na+ and protons.The study of the system in the presence of added NaCl, KCl, and CsCl provided further test for the kinetic model as well as the estimation of other ion-exchange constants.
Visible-Light-Induced C4-Selective Functionalization of Pyridinium Salts with Cyclopropanols
Hong, Sungwoo,Kim, Taehwan,Vellakkaran, Mari
supporting information, (2021/11/27)
The site-selective C?H functionalization of heteroarenes is of considerable importance for streamlining the rapid modification of bioactive molecules. Herein, we report a general strategy for visible-light-induced β-carbonyl alkylation at the C4 position of pyridines with high site selectivity using various cyclopropanols and N-amidopyridinium salts. In this process, hydrogen-atom transfer between the generated sulfonamidyl radicals and O?H bonds of cyclopropanols generates β-carbonyl radicals, providing efficient access to synthetically valuable β-pyridylated (aryl)ketones, aldehydes, and esters with broad functional-group tolerance. In addition, the mild method serves as an effective tool for the site-selective late-stage functionalization of complex and medicinally relevant molecules.
N-Aroylsulfonamide-Photofragmentation (ASAP)-A Versatile Route to Biaryls
Wessig, Pablo,Krebs, Saskia
supporting information, p. 6367 - 6374 (2021/09/29)
The photochemical fragmentation of N-aroylsulfonamides 9 (ASAP) is a powerful method for the preparation of various biaryls. Compounds 9 are easily accessible in two steps from amines by treatment with arenesulfonyl chlorides and aroyl chlorides. Many of these compounds were prepared for the first time. The irradiation takes place in a previously developed continuous-flow reactor using inexpensive UVB or UVC fluorescent lamps. Isocyanates and sulphur dioxide are formed as the only by-products. The ASAP tolerates a variety of functional groups and is even suited for the preparation of phenylnaphthalenes and terphenyls. The ASAP mechanism was elucidated by interaction of photophysical and quantum chemical (DFT) methods and revealed a spirocyclic biradical as key intermediate.