Reactivity patterns of N-methylbenzhydroxamates. I. Studies of methyl transfer between N-methylbenzhydroxamates and arenesulfonates

Abstract

. Can. J. Chem. 69,798 (1991).The rates of methyl transfer between benzohydroxamates and sulfonates show large Pnuc values (ca. 0.8) indicating much charge transfer to the C atom, similar to the results of N,N-dialkylaminofluorene anions. A small a effect shows that even in methyl substrates, with certain leaving groups, the effect is displayed. Investigation of the PI, shows that from the leaving group side of the reaction it is a normal SN2 reaction. Correlation of the reactivity with computed gas phase ionization potentials shows that desolvation of anions is probably not important. These results suggest an a-effect model that explains the larger size of the effect at carbonyl groups in terms of greater solvation of the charge transferred to the 0 atom. anions N,N-dialkylaminofluor&nes. Un faible effet a montre que, m&me avec des substrats mCthyles de certains nuclCofuges, on peut observer cet effet. Une Ctude du PI, montre que, par rapport au groupement nuclCofuge, il s'agit d'une reaction SN2 normale.Une corrClation de la rCactivitt avec les potentiels d'ionisation en phase gazeuse calculks montre que la dksolvatation des anions n'est probablement pas importante. Ces rCsultats suggkrent un modkle d'effet a qui explique l'importance plus grande de l'effet au niveau des groupements carbonyles en termes de plus grande solvatation de la charge qui est transfkrke i l'atome d'oxygkne.Mots clis : effet a , courbe de Bransted, potentiels d'ionisation, voltamktrie cyclique, PI,, P,,,, AMl, E4.[Traduit par la rCdaction]

The α-Effect in Benzyl Transfers from Benzylphenylmethyl Sulfonium Salts to N-Methylbenzohydroxamate Anions

“…Sodium salts of N -methylbenzohydroxamic acids (NMBH) were made as previously reported, and their p K a values in MeOH are available from prior studies. , Phenolate salts were made for reactions of NaOCH 3 in methanol with the respective phenols and NaOMe.…”

“…Kinetics for [2] were obtained analogously to our previous method for methyl transfers. , Table shows the results as rate constants.…”

“…Recent reports − show that N -methylbenzohydroxamate (NMBH) anions display an α-effect of ca. 2−10 (rate constant ratios) in methyl transfers from arylsulfonate ions and arylmethyl thioethers, [1].…”

O-Alkylation of N-Phenylhydroxylamine in Dimethyl Sulfoxide with Methylarenesulfonates

“…The reactivity of substituted NPHA and N -methylanilines vs. substituted methylarenesulfonates in DMSO- d 6 , reaction1, was measured by our published kinetic method on a Varian XL200 NMR. , Table summarizes the results. A Hammett plot of log k nuc for methylation with methylarenesulfonate ester in DMSO, Figure , shows a ρ value of −1.70.…”

Palladium-catalysed direct heteroarylation of bromobenzenes bearing SO2R substituents at C2 or C4

“…From 4-bromo-N-phenylbenzenesulfonamide (0.312 g, 1 mmol) and ethyl 2-methylfuran-3-carboxylate (0.231 g, 1.5 mmol), product 17 was obtained in 66% (0.254 g) yield. 1 Phenyl 4-(2-propylthiazol-5-yl)-benzenesulfonate (19). From phenyl 4-bromobenzenesulfonate (0.313 g, 1 mmol) and 2-propylthiazole (0.190 g, 1.5 mmol), product 19 was obtained in 90% (0.323 g) yield.…”