GAS-PHASE NITRATION OF THIOPHENE AND N-METHYLPYRROLE BY PROTONATED ALKYL NITRATES

被引:1
作者
ATTINA, M
机构
[1] Dipartimento di Chimica e Tecnologia delle Sostanze Biologicamente Attive, Università di Roma 'La Sapienza, Rome, 00185
关键词
D O I
10.1002/poc.610030207
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
Gas‐phase nitration of thiophene (1) and N‐Methylpyrrole (2) was studied by radiolytic tecniques, supported by chemical ionization mass spectrometry. The substrate and positional selectvities of protonated alkyl nitrtes (CH3NO3H+, CF3CH2NO3H+) were deduced from competitive reactions with bezene performed under different conditions. The apparent kS/kB ratios, which are independent of the pressure and unaffected by the presence of a strong base (NEt3), depend on the nature of the electrophile, passing for 1 and 2 from 7·2 and 6·4, respectively, with CH3NO3H+ to 1·1 and 1·0, respectively, with the more reactive fluorinated caution. Predominant (88%) α‐substitution takes place in 1, whereas no appreciable positional discrimination is displaced by 2. The results suggest that the electrophilic attack can also occur a the heteroatom, and point to the same mechanism postulated for gasphase nitration of aromatic substrates, the reactivity being essentially governed by electrostatic interactions within the ‘encounter pair’. Copyright © 1990 John Wiley & Sons Ltd.
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页码:110 / 118
页数:9
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