Transformations of para-Substituted Benzylcyclopropanes, Allylbenzenes, and Diphenylmethanes under Nitration with Nitric Acid in Acetic Anhydride

Abstract

Electrophilic nitration of benzylcyclopropanes, allylbenzenes, and diphenylmethanes containing ortho,para-orienting substituents in the para position of the benzene ring results mainly in replacement of the cyclopropylmethyl, allyl, or benzyl group, respectively (ipso substitution). The nitration of 4-cyclopropylallylbenzene is not accompanied by nitrodealkylation, and the products are only 2-and 3-nitro-4-cyclopropylallylbenzenes.Up to now, direct proofs have been obtained that electrophilic nitration of p-alkyl-and p-alkoxysubstituted toluenes and phenylcyclopropanes I-III involves intermediate formation of ipso-σ-complexes IV-VI which are then converted into relatively stable cyclohexadiene adducts VII-IX (Scheme 1) [1-10]. Adducts like VII-IX can be isolated; however, they usually undergo acid-catalyzed transformations during the process. These transformations give rise to not only conventional electrophilic substitution products but OMe III HNO 3 /Ac 2 O NO 2 OMe

Characterizing Covalently Sidewall-Functionalized Single-Walled Carbon Nanotubes by Using1H NMR Spectroscopy

“… * σ m , σ o = Hammett constant for meta and ortho positions, respectively. a Reference . b σ o for COOH. c Reference . d Reference . e Reference . f Reference . g Accidental coincidence. …”

“… a Reference . b Reference . * Δ = Difference in chemical shifts of protons of SWCNT–Ph–NO 2 relative to substituted benzenes (δ SWCNT–Ph–NO 2 – δ R‑Ph–NO 2 ). …”

“… Δ = Difference in chemical shifts of protons of SWCNT-Ph-NO 2 relative to substituted benzenes (δ SWCNT-Ph-NO2 - δ R-Ph-NO2 ). a Ref 45. b Ref 47. …”