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Cleavage of the Oxanorbornene Oxygen Bridge with Lewis Acids: Computation and Experiment

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Abstract
Since the discovery of the biological activity of aminophosphonates, research started on the synthesis of more constraint azaheterocyclic phosphonates. We developed a route via an intramolecular Diels-Alder reaction towards α-aminophosphonates 1. [1] The obtained oxanorbornene skeleton is a valuable synthetic intermediate that has been used in various natural product syntheses. [2] An important synthetic transformation involves the cleavage of the oxygen bridge, used to construct substituted arenes and cyclohexenes. We wanted to investigate the ring opening of adducts 1 using different Lewis acids experimentally and get more insight in the reaction pathways towards the different products via computational experiments. In this presentation the results obtained with TiCl4 and FeCl3 catalyst are shown. The computational study started with the catalysts and their multiplicity. Next, the complexation energy with different binding sites was calculated. Therefore, a level of theory study was done using an ONIOM QM/QM approach. This shows the importance of the inclusion of electron correlation effects. B3LYP geometries and energies can be used as a good approximation. Bidentate coordination towards the most electronegative phosphonate oxygen and the oxygen bridge is favoured for both catalysts. Then, different reaction pathways were investigated via a static, gas-phase approach. The energy barrier towards the transition state using the TiCl4 catalyst, shown in Figure 1, is much lower than for the FeCl3 catalyst and very different products are formed. The computational results were compared with the experiments.

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Chicago
Claeys, Diederica, K. Moonen, Bart Roman, Pieter Van de Caveye, Veronique Van Speybroeck, Michel Waroquier, and Christian Stevens. 2009. “Cleavage of the Oxanorbornene Oxygen Bridge with Lewis Acids: Computation and Experiment.” In Abstracts 13th ICQC Congress, 215.
APA
Claeys, Diederica, Moonen, K., Roman, B., Van de Caveye, P., Van Speybroeck, V., Waroquier, M., & Stevens, C. (2009). Cleavage of the Oxanorbornene Oxygen Bridge with Lewis Acids: Computation and Experiment. Abstracts 13th ICQC Congress (p. 215). Presented at the 13th ICQC Congress.
Vancouver
1.
Claeys D, Moonen K, Roman B, Van de Caveye P, Van Speybroeck V, Waroquier M, et al. Cleavage of the Oxanorbornene Oxygen Bridge with Lewis Acids: Computation and Experiment. Abstracts 13th ICQC Congress. 2009. p. 215.
MLA
Claeys, Diederica, K. Moonen, Bart Roman, et al. “Cleavage of the Oxanorbornene Oxygen Bridge with Lewis Acids: Computation and Experiment.” Abstracts 13th ICQC Congress. 2009. 215. Print.
@inproceedings{765741,
  abstract     = {Since the discovery of the biological activity of aminophosphonates, research started on the synthesis of more constraint azaheterocyclic phosphonates. We developed a route via an intramolecular Diels-Alder reaction towards \ensuremath{\alpha}-aminophosphonates 1. [1] The obtained oxanorbornene skeleton is a valuable synthetic intermediate that has been used in various natural product syntheses. [2] An important synthetic transformation involves the cleavage of the oxygen bridge, used to construct substituted arenes and cyclohexenes. We wanted to investigate the ring opening of adducts 1 using different Lewis acids experimentally and get more insight in the reaction pathways towards the different products via computational experiments. In this presentation the results obtained with TiCl4 and FeCl3 catalyst are shown.

The computational study started with the catalysts and their multiplicity. Next, the complexation energy with different binding sites was calculated. Therefore, a level of theory study was done using an ONIOM QM/QM approach. This shows the importance of the inclusion of electron correlation effects. B3LYP geometries and energies can be used as a good approximation. Bidentate coordination towards the most electronegative phosphonate oxygen and the oxygen bridge is favoured for both catalysts. Then, different reaction pathways were investigated via a static, gas-phase approach. The energy barrier towards the transition state using the TiCl4 catalyst, shown in Figure 1, is much lower than for the FeCl3 catalyst and very different products are formed. The computational results were compared with the experiments.},
  author       = {Claeys, Diederica and Moonen, K. and Roman, Bart and Van de Caveye, Pieter and Van Speybroeck, Veronique and Waroquier, Michel and Stevens, Christian},
  booktitle    = {Abstracts 13th ICQC Congress},
  language     = {eng},
  location     = {Helsinki, Finland},
  title        = {Cleavage of the Oxanorbornene Oxygen Bridge with Lewis Acids: Computation and Experiment},
  year         = {2009},
}