Dearomative (3+2) cycloaddition of 2-substituted 3,5-dinitropyridines and N-methyl azomethine ylide

Nitropyridines as 2π-Partners in 1,3-Dipolar Cycloadditions with N-Methyl Azomethine Ylide: An Easy Access to Condensed Pyrrolines

“…In addition, in the presence of an amine moiety in position 2 (compounds 2c, 2j, 2n, 2q), the reaction also does not proceed. This reactivity is most likely associated with the electron-donor effect of the amino group, which reduces the overall electrophilicity of the starting compound [20,21]. The target product was isolated only for compound 2f where conversion of the starting pyridine was about 50% according to the NMR spectroscopy data.…”

“…We found that this reaction resulted in the addition of two molecules of a dipole to the pyridine nucleus with the formation of compound 5. It is known that, in similar reactions, the addition of a dipole occurs from the opposite sides of the benzene (pyridine) ring, providing trans-cycloadducts [19,20,22,23]. However there are examples of the formation of cis-cycloadducts [24].…”

“…The full assignment of hydrogen and carbon atoms in NMR spectra was made. The 1 H-1 H NOESY spectrum of 5 contains a characteristic cross-peak corresponding to the interaction of spatially close H(1) and H(6) It is known that, in similar reactions, the addition of a dipole occurs from the opposite sides of the benzene (pyridine) ring, providing trans-cycloadducts [19,20,22,23]. However there are examples of the formation of cis-cycloadducts [24].…”

“…Earlier, we reported on the development of a method for the synthesis of pyrrolidine and pyrroline derivatives condensed with a pyridine ring on the basis of 2-R-3,5-dinitropyridines [19,20]. It was shown that, depending on the nature of 2-R, annulation of either two pyrrolidine rings or one pyrroline ring is possible [20], Scheme 1. Scheme 1.…”

Synthesis and Facile Dearomatization of Highly Electrophilic Nitroisoxazolo[4,3-b]pyridines

“…At the same time, dearomatization as a method of converting accessible, cheap, and simple aromatic compounds into more saturated, inaccessible and promising intermediates of greater molecular complexity is a very important approach in modern organic chemistry [36,37]. This work is part of our ongoing research on highly electrophilic systems and the application of the dearomatization strategy in the synthesis of new polyfunctional azaheterocycles [38][39][40][41][42][43][44][45][46][47][48]. We have previously shown that nitropyridines fused with π-deficient heterocycles (furoxan A, selenadiazole B), Scheme 1, react with neutral nucleophiles with the formation of 1,4-addition productsdihydropyridine derivatives [45,46,48].…”