A reliable method for the synthesis of bis-spirocyclic derivatives of 3-azabicyclo[3.1.0]hexane through the 1,3-dipolar cycloaddition (1,3-DC) reactions of cyclopropenes to the stable azomethine ylide – protonated form of Ruhemann's Purple (PRP) has been developed. Both 3-substituted and 3,3-disubstituted cyclopropenes reacted with PRP, affording corresponding bis-spirocyclic 3-azabicyclo[3.1.0]hexane cycloadducts in moderate to good yields with high diastereofacial selectivity. Moreover, several unstable 1,2-disubstituted cyclopropenes were successfully trapped by the stable 1,3-dipole under mild conditions. The mechanism of cycloaddition reactions of cyclopropenes with PRP has been thoroughly studied using density functional theory (DFT) methods at the M11/cc-pVDZ level of theory. The cycloaddition reactions have been found to be HOMOcyclopropene – LUMOylide controlled while transition-state energies for the reaction of 3-methyl-3-phenylcyclopropene with PRP are fully consistent with the experimentally observed stereoselectivity.
Keywords: azomethine ylides, cycloaddition, cyclopropenes, DFT calculations, spiro heterocycles
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Stepakov, A.; Filatov, A.; Khoroshilova, O.; Larina, A.; Boitsov, V. Beilstein Arch. 2022, 20227. doi:10.3762/bxiv.2022.7.v1
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