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Journal Article

Cyclization of an α,β-Unsaturated Hydrazone Catalyzed by a BINOL-Phosphoric Acid: Pericyclic or Not?

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Heggen,  Berit
Research Department Thiel, Max-Planck-Institut für Kohlenforschung, Max Planck Society;

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Thiel,  Walter
Research Department Thiel, Max-Planck-Institut für Kohlenforschung, Max Planck Society;

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jcc24044-sup-0001-suppinfo.pdf
(Supplementary material), 303KB

Citation

Heggen, B., Patil, M., & Thiel, W. (2016). Cyclization of an α,β-Unsaturated Hydrazone Catalyzed by a BINOL-Phosphoric Acid: Pericyclic or Not? Journal of Computational Chemistry, 37(2), 280-285. doi:10.1002/jcc.24044.


Cite as: https://hdl.handle.net/11858/00-001M-0000-0029-5625-7
Abstract
Density functional theory is used to study the mechanism of the title reaction, one of the first catalytic asymmetric 6π-electrocyclizations observed experimentally. The benzylideneacetone-derived phenyl hydrazone is chosen as model substrate for the cyclization reaction, both in the protonated (A) and unprotonated (B) form, while the isoelectronic carbon analogue, 1,5-diphenylpentadienyl anion (C), serves as a reference for comparisons. The barrier to cyclization is computed to be more than 15 kcal/mol lower in A compared with B, in line with the observed acid catalysis. The relevant transition states to cyclization are characterized for A and C using orbital inspection, natural bond orbital analysis, nucleus independent chemical shifts, and stereochemical indicators. The cyclization of C is confirmed to be pericyclic, while that of A can be described as pseudopericyclic ring closure involving an intramolecular nucleophilic addition.