Additionsreaktionen der nitrosogruppe—XIV

The Diels–Alder Reaction of 4,6‐Dinitrobenzofuroxan with 1‐Trimethylsilyloxybuta‐1,3‐diene: A Case Example of a Stepwise Cycloaddition

“…[16][17][18] This is exemplified in Scheme 1, which shows that the reaction of DNBF with cyclopentadiene (Cp) in dichloromethane at room temperature initially affords a 1:1 mixture of the [2 + 4] and [4 + 2] monoadducts 4 and 5 in their racemic forms.…”

NMR Spectroscopy: A Useful Tool in the Determination of the Electrophilic Character of Benzofuroxans - Case Examples of the Reactions of Nitrobenzofuroxans with Dienes and Nucleophiles

“…For example, for an IEDDA adducts, the 1 H NMR spectra show a deshielded signal at 6 ppm typical of H 11 and a multicoupled signal at 4 ppm typical of H 10 (see Figure 3) while 13 C NMR spectra show that the signals pertaining to carbon 7, 10, 14 are found to be at higher field in the case of IEDDA adducts than in the case of NEDDA adducts. For these latter adducts, the 1 H NMR spectra exhibited broad signals at 3.5 ppm pertaining to H 10 …”

“…There is little doubt that these species correspond to the products isolated in 1973 by Kresze and Bathelt. 10 At this time, however, no attempt was made to elucidate the stereochemistry and the mechanistic course of the reactions.…”

“…Crucial evidence for this relationship has been the discovery that the nitro-activated double bonds of this ring behave similarly to nitroalkene fragments in a variety of Diels-Alder processes, acting as dienophiles or heterodienes depending upon the reaction partner and the experimental conditions at hand. [10][11][12][13][14][15][16] A first illustrative sequence refers to the reaction of ANBF with cyclohexadiene. Reflecting the potential 1-oxide/3-oxide interconversion of benzofuroxans through the intermediacy of an o-dinitroso intermediate, 15 diadducts 5 resulting from normal electron-demand Diels-Alder (NEDDA) processes involving the N=O double bonds of such intermediates as the dienophile contributors have also been isolated.…”

“…On the other hand, the preferred formation of the unsymmetrical IEDDA-NEDDA adduct 12 implies a greater dienophilic reactivity of the remaining nitroolefinic moiety in the IEDDA adduct 11 than in the NEDDA adduct 10. [10][11][12][13][14][15][16] 3.2 Elucidation of the reaction of DNBF with 2,3-dimethylbutadiene.…”