The intramolecular selectivity of the electrophilic reactions of Et+, i-Pr+, and Me2F+ cations with substituted anilines, including m-toluidine, m-anisidine, and m- and p-fluoroaniline, has been investigated in the dilute gas state at pressures ranging from 100 to 720 torr by a radiolytic technique, complemented by chemical ionization mass spectrometry. The results indicate an appreciable kinetic bias for the nitrogen atom, leading to predominant N-methylation by Me2F+. The reactivity of the carbenium ions is complicated by the simultaneous Occurrence of proton transfer, in particular to the NH2 group, which increases the relative extent of ring alkylation. The positional selectivity is characterized, aside from the usual orienting effects of the substituents, by the enhanced reactivity of the ring positions ortho to an n-type substituent, irrespective of its activating or deactivating properties. The effect is traced to the preliminary formation of an electrostatic adduct between the aniline and the gaseous electrophile.
Intramolecular selectivity of the alkylation of substituted anilines by gaseous cations / Marina, Attina; Cacace, Fulvio; DE PETRIS, Giulia. - In: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. - ISSN 0002-7863. - STAMPA. - 107:6(1985), pp. 1556-1561. [10.1021/ja00292a017]
Intramolecular selectivity of the alkylation of substituted anilines by gaseous cations
CACACE, Fulvio;DE PETRIS, GIULIA
1985
Abstract
The intramolecular selectivity of the electrophilic reactions of Et+, i-Pr+, and Me2F+ cations with substituted anilines, including m-toluidine, m-anisidine, and m- and p-fluoroaniline, has been investigated in the dilute gas state at pressures ranging from 100 to 720 torr by a radiolytic technique, complemented by chemical ionization mass spectrometry. The results indicate an appreciable kinetic bias for the nitrogen atom, leading to predominant N-methylation by Me2F+. The reactivity of the carbenium ions is complicated by the simultaneous Occurrence of proton transfer, in particular to the NH2 group, which increases the relative extent of ring alkylation. The positional selectivity is characterized, aside from the usual orienting effects of the substituents, by the enhanced reactivity of the ring positions ortho to an n-type substituent, irrespective of its activating or deactivating properties. The effect is traced to the preliminary formation of an electrostatic adduct between the aniline and the gaseous electrophile.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.