Reactions of 1,2- and 1,3-Dimethoxy- and 1,3,5-Trimethoxybenzene with Nitrogen Dioxide/Dinitrogen Tetraoxide in Dichloromethane

Abstract

The products of reaction of nitrogen dioxide/dinitrogen tetraoxide with dichloromethane solutions of three different methoxybenzenes are studied and interpreted in terms of initial nitrosation followed by oxidation with nitrogen dioxide.

Metal‐free Transformations of Nitrogen‐Oxyanions to Ammonia via Oxoammonium Salt

“…The X‐ray crystal structure of 2 b exhibits a planar oxoammonium nitrogen (N1) with N1−O5 1.2587(16) Å comparable to that in 2 a (Figure S20). Thus, these results unequivocally demonstrate the identity of the subtle diaryl oxoammonium species 2 b , which was erroneously formulated in the previous literature due to its relative instability [16c] . Interestingly, reactions of 1,4‐dimethoxybenzene ( 1 e ) and 1,2,4‐trimethoxybenzene ( 1 f ) with t BuONO or NO 2 in dichloromethane solely lead to electrophilic aromatic nitration affording respective nitro derivatives in near quantitative yields (Figure 2).…”

“…Notably, previous reports on the electrophilic nitration of TMB−H ( 1 a ) and DMB−H ( 1 b ) by HNO 3 or NO 2 have indicated the generation of intense blue and green colored species, respectively [16] . The previous studies also suggest that the nitration of methoxy‐arenes typically yields a mixture of products including a rare diaryl oxoammonium salt along with the expected nitro‐derivative [16c] . In addition to the CHN analysis, 1 H NMR, FT‐IR, and UV/Vis characterizations of the diaryl oxoammonium species [TMB 2 N + =O][NO 3 − ] ( 2 a ), [16c] a X‐ray crystal structure of 2 a has been reported recently [16d] .…”

“…The previous studies also suggest that the nitration of methoxy‐arenes typically yields a mixture of products including a rare diaryl oxoammonium salt along with the expected nitro‐derivative [16c] . In addition to the CHN analysis, 1 H NMR, FT‐IR, and UV/Vis characterizations of the diaryl oxoammonium species [TMB 2 N + =O][NO 3 − ] ( 2 a ), [16c] a X‐ray crystal structure of 2 a has been reported recently [16d] . In contrast, 1 H NMR, FT‐IR, and UV/Vis characterizations of the metastable diaryl oxoammonium species [DMB 2 N + =O][NO 3 − ] ( 2 b ), in the previous literature, have been found to be inadequate and resulted in an erroneous formulation due to the difficulty in determining the exact elemental composition [16c] .…”

“…In addition to the CHN analysis, 1 H NMR, FT‐IR, and UV/Vis characterizations of the diaryl oxoammonium species [TMB 2 N + =O][NO 3 − ] ( 2 a ), [16c] a X‐ray crystal structure of 2 a has been reported recently [16d] . In contrast, 1 H NMR, FT‐IR, and UV/Vis characterizations of the metastable diaryl oxoammonium species [DMB 2 N + =O][NO 3 − ] ( 2 b ), in the previous literature, have been found to be inadequate and resulted in an erroneous formulation due to the difficulty in determining the exact elemental composition [16c] . Hence, the detailed characterizations of such species by complementary methods and establishment of their spectroscopic signatures are crucial.…”

“…[NO + ][BF 4 − ], t BuONO, NO 2 , NO x − /H + ) conveniently provide the diaryl oxoammonium species 2 a instead of aromatic nitration yielding nitroaromatics. While the chemistry of aliphatic oxoammonium species is relatively well known, [19, 22] the structure–reactivity profile of analogous diaryl oxoammonium species remains elusive [16c, 23] …”