Thermolysis of dimethyl cis- and trans-1 pthalimidoaziridine-2,3-dicarboxylates in the presence of dipolarophiles

Intra- and intermolecular thermal transformations of 2-acyl- and 2-alkoxycarbonyl-N-phthalimidoaziridines

“…As already noted in our previous work [4,5], the reaction of trans-disubstituted aziridines 1a,d, and 1e with N-phenylmaleimide leads to exo-adducts with cis orientation of the substituents at the carbon atoms of the former aziridine ring, which is in accord with the reaction scheme given below.…”

“…The invertomers of aziridine 1e exist in comparable amounts since the effective volumes of the substituents at the carbon atoms of the aziridine ring in this case are similar (both substituents have a carbonyl group next to the three-membered ring). The coupling constants of compounds 1a,d, and 1e (4.4-4.9 Hz for the major invertomer and 4.7-5.8 Hz for the minor invertomer) indicate trans arrangement of the aziridine protons, which is in accord with the well-known steric specificity of oxidative aminoaziridination [3][4][5][6][7][8][9][10]. We should also note that the signals of the phthalimide group carbon atoms in the 13 C NMR spectra of aziridines 1a-f are broadened as a consequence of a second hindered process, which is slow on the NMR time scale, namely, rotation about the tetrasubstituted N-N bond [4,5,10].…”

“…The addition of these species at multiple bonds of dipolarophiles yields various five-membered nitrogen heterocycles [2]. The generation of azomethinylids upon heating derivatives of N-phthalimidoaziridine and subsequent 1,3-dipolar cycloaddition have been demonstrated experimentally [3][4][5]. On the other hand, heating N-phthalimidoaziridines having acyl [6] or alkoxycarbonyl substituents [7] at the carbon atoms of the aziridine ring in the absence of dipolarophiles leads to oxazoles, which may be attributed to a 1,5-electrocyclization of the intermediate acylazomethinylids accompanied by loss of the phthalimide group.…”

Synthesis and Spectroscopic and Electrochemical Properties of an Axially Symmetric Fullerene–Porphyrin Dyad with a Rigid Pyrrolo[3,4-c]pyrrole Spacer

“…The stereochemistry of cycloadduct 12 was confirmed by the observance of four signals (3.66, 4.01, 4.93, and 5.11 ppm) for the pyrrolidine protons in the 1 H NMR spectrum, meaning that it has C 1 symmetry and this is only possible if the relative configurations of the stereocenters in the 2,4- and 3,5-positions of the pyrrolidine ring are different. In addition, chemical shifts and spin–spin coupling constants in compound 13 are very close to those in similar compounds of known configuration …”

“…In addition, chemical shifts and spin−spin coupling constants in compound 13 are very close to those in similar compounds of known configuration. 45 A number of reagents have been tested under various conditions to find the optimal way for aromatization of cycloadduct 12 to pyrrole 13. The reaction did not proceed with sulfur as oxidant under conventional heating or microwave irradiation.…”