Nitration of the tetramethylbenzenes in acetic anhydride. Formation and rearomatization of adducts

Abstract

Nitration of the tetramethylbenzenes in acetic anhydride at temperatures below –50 °C gives the l-acetoxy-4-nitro and 5-acetoxy-2-nitro adducts from the 1,2,3,4 isomer, the 5-acetoxy-2-nitro adduct from the 1,2,3,5 isomer, and the l-acetoxy-4-nitro adduct from the 1,2,4,5 isomer as well as the expected nitro derivatives. Corresponding nitritonitro adducts are also formed as well as side-chain (benzylic) derivatives: nitrates and phenylnitromethanes. Rearomatization of the tertiary acetate adducts leads to aryl acetates, benzylic derivatives, or nitroarenes, depending upon the acidity of the solvent. In the benzylic derivatives the methyl group substituted is that ipso to the acetate in the precursor adduct, that para to the most activated ipso position of the arene.

Wavelength-dependent photochemistry of a diazo compound. Irradiation of 9-diazo-1,8-diazafluorene with ultraviolet or visible light

“…T. H. "Ratio of the yield of cyclopropane 2 to norcaradiene 3 determined by gas chromatography. 6 Yield of the cyclopropane 2 (%). = Yield of the diazirine 1 (%).…”

“…Thus, R ranges from 1.0 for complete retention to 0.0 for total randomization of the olefin configuration. R = (retainedinverted)/(retained + inverted) (6) Shown in Figure 2 are double-reciprocal plots of R against the concentration of AMS for irradiation of 18DAF at 310 and at 420 nm in HFB solution. Several facts are apparent from inspection of these plots.…”

Nitration of p-tert-butyltoluene in acetic anhydride. 1,2 and 1,4 adducts

“…General experimental methods have been described previously (2). p-Tolyl acetate was obtained by acetylation ofp-cresol; nmr (CDC13) .T 2.90 (d, 2, 2-H and 6-H), 3.08 (d, 2, 3-H and 5-H), 7.72 (s, 3, 4-CH3).…”

“…Addition of acetyl nitrate (as nitronium acetate) t o appropriately substituted arenes, initiated by addition of the nitronium ion at an ipso (1) position, is well established (2)(3)(4). The present study is a continuation of our investigations of the formation and rearomatization reactions of adducts of 4-alkyltoluenes.…”

“…A distinguishing feature of this series is that the adducts are tertiary acetates. Other arenes which have been shown to give tertiary acetate adducts are 1,2,4-trimethylbenzene (pseudocumene) (8) and the tetramethylbenzenes (2). Toluene (9) and o-xylene (10) give secondarv acetate adducts.…”