Unexpected direction of the reaction ofo-dinitrobenzene and benzofuroxane witht-BuNHMgBr

Abstract

In the reaction of 1 with 3, we might have expected the formation of bis(t-butylazoxy)benzene, by analogy to our previous results [1], or nucleophilic substitution of one of the nitro groups since N-t-butyl-2-nitroaniline is obtained upon heating 1 with t-BuNH 2 in ethanol at reflux. The observed formation of 4 occurs through intermediate 5 due to the partial reduction of one of the nitro groups with subsequent conversion of the nitroso and nitro groups in 5 into the corresponding azo and azoxy moieties. Such a reaction course was supported by an independent experiment, in which 4 was obtained by the reaction of 3 with 5 synthesized according to Heckler [2] under the same conditions as for the reaction of 3 with 1. The formation of 4 in the reaction of 2 with 3 apparently results from the initial opening of the furoxane ring due to nucleophilic attack of 3 on the nonoxygenated nitrogen atom in 2 with generation of the corresponding o-nitrohydrazobenzene [3], subsequent transformation of the nitro group into an azoxy group, and oxidation of the hydrazo fragment to an azo fragment [4]. There were no indications of the formation of o-bis(t-butylazo)benzene in the reaction of 2 with 3 although 2 is known to react as a dinitroso derivative [5], while nitrosobenzene reacts with 3 to give t-butylazobenzene [1]. The synthesis of ~1 from 1 and 2 was carried out in accord with our previous procedure and the product was purified by chromatography on a silica gel column. The NMR spectra were taken in CDC13 on a Bruker AM-300 spectrometer. 1-(t-Butylazoxy)-2-(t-butylazo)benzene (4) was obtained as a viscous brown liquid, nD 24 1.5275. Found, %: C 64.21; H 8.45; N 21.52. CI4H22N40. Calculated, %: C 64.12; H 8.40; N 21.7%. PMR spectrum (~, ppm, TMS): 7.34-7.43 m (3H, H 3, H 4, Hs), 7.56-7.59 m (1H, 1-16). 13C NMR spectrum (8, ppm, TMS): 25.7 (Me3, azo), 26.8 (Me 3, azoxy), 60.0 [N(O)-N-C] , 69.0 (N~--N-C), 143.9 (C1), 147.4 (C2), 17.3 (C3), 130.1 (C4), 129.95 (C5), 123.4 (C6). 14N NMR spectrum (8, ppm, MeNO2): -51 .6 [ N ( O ) ~ ] . 15N NMR spectrum (6, ppm, MeNO~: + t77.7 ( N = N , INEPT from CMe3).