The formation and reactions of adducts formed in the nitration of p-diethylbenzene
Date
1978
Authors
Thompson, Robert James
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Abstract
Nitration of 𝑝-diethylbenzene by acetyl nitrate in acetic anhydride at -45°C gives the diastereoisomeric l,4-diethyl-4-nitrocyclohexa-2,5-dienyl acetates (IA and IB), 1-(p-ethylphenyl)-nitroethane (II), and 2,5-diethylnitrobenzene (III). The stereochemistry of the acetoxynitro adducts was studied using the n.m.r. shift reagent, tris-(1,l,l,2,2,3,3-heptafluoro-7,7-dimethyl-d6-4,6-octane-dionato)-europium. The formation of the dienyl adducts and the side-chain nitre product through the ipso attack of nitronium ion at the carbon bearing an ethyl group is discussed. The reactions of the ipso-cation, l,4-diethyl-l-nitrocyclohexa-2,5-dienyl carbonium ion (IV) with water to form the l,4-diethyl-4-nitrocyclohexa-2,5-dienols (V), with methanol to form the dienyl methyl ethers (VI), and with acetic acid-d4 to form the trideuterated analogues (VII) of I are presented.
The reactions of I under conditions which promote rearomatisation have been studied and discussed in terms of formation of IV or l-acetoxy-l,4-diethylcyclohexa-2,5-dienyl cation (VIII). Rearomatisation of I under acidic conditions gives III and p -ethylacetophenone (IX) derived from side-chain substituted products. Rearomatisation of I in aqueous methanol gives 2,5-diethylphenyl acetate (X) and methanolic sodium methoxide solvolysis of I gives V which rearomatises with a 1,2-alkyl shift to give 2,4-diethyl-phenol (XI).