What Controls Regiochemistry in 1,3-Dipolar Cycloadditions of Münchnones with Nitrostyrenes?
ABSTRACT The distinct experimentally observed regiochemistries of the reactions between mesoionic münchnones and β-nitrostyrenes or phenylacetylene are shown by DFT/BDA/ETS-NOCV analyses of the transition states to be dominated by steric and reactant reorganization factors, rather than the orbital overlap considerations predicted by Frontier Molecular Orbital (FMO) Theory.
SourceAvailable from: Jerry P. Jasinski[Show abstract] [Hide abstract]
ABSTRACT: In the title compound, C26H23NO2, the dihedral angles between the pyrrole ring and the two phenyl rings are 58.1 (6) and 71.5 (5)°. The mean planes of the 5-methyl-benzene ring and the carboxyl group are twisted by 89.5 (3) and 22.1 (9)°, respectively, from the pyrrole ring. In the crystal, weak C-H⋯O inter-actions lead to supra-molecular layers in the ab plane.Acta Crystallographica Section E Structure Reports Online 03/2014; 70(Pt 3):o338-9. DOI:10.1107/S1600536814003316 · 0.35 Impact Factor
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ABSTRACT: The applications of nitroalkenes in the synthesis of three- to five-membered O, N and S-heterocycles, including natural products are investigated in this review. These heterocyclic compounds were synthesized from nitroalkenes with a variety of substituents at α and β-positions and those that are part of common and medium rings via a wide variety of reactions such as Michael addition, epoxidation, [3+2] cycloaddition and many cascade/domino/tandem reactions. In addition, the potential of nitroalkenes to take part in multi-component and cascade reactions, particularly, in diastereo- and enantioselective versions are reviewed. The high reactivity of nitroalkenes and their potential to coordinate the metal catalysts as well as organocatalysts signify them as efficient precursors in synthetic organic chemistry. Also, the flexibility of nitro group in functional group manipulations has expanded the scope of nitro group, in general, and nitroalkenes, in particular, in organic synthesis.RSC Advances 09/2014; 4(89). DOI:10.1039/C4RA08828J · 3.71 Impact Factor
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ABSTRACT: A diastereoselective (3 + 2) dearomative annulation of 3-substituted indoles with α-haloketones has been developed. Significant regiochemical control was observed. This methodology provides easy access to highly functionalized cyclopenta- or cyclohexa-fused indoline compounds, which are common structures of many natural products. The synthetic potential of this reaction was demonstrated in the concise syntheses of the core structures of vincorine, isocorymine, and aspidophylline A. DFT studies (B3LYP-D3/6-311++G**/MeOH) on cyclization mechanisms involving the 2-hydroxyallyl cation and its deprotonated oxyallyl cation have been performed. Under the reaction conditions, with a sparingly soluble Na2CO3 base, both species may be present and both pathways are viable. Both pathways support the formation of the experimentally observed O-bound intermediate, its transformation to the final product, the regiochemical and eventual stereochemical outcome of the kinetic cyclization product, and the thermodynamic preference for formation of the final stereoisomer.Journal of the American Chemical Society 04/2014; 136(17):6288-6296. DOI:10.1021/ja412435b · 11.44 Impact Factor