Title

Halogen Bonding

Presenter Information

George F. Neuhaus Mr.Follow

Presentation Type

Poster

Abstract

Halogen bonds are non-covalent attractive interactions between halogens that are covalently bound to organic structures, and Lewis bases (species with areas of high electron density). This attraction is caused by an electron-deficient group that is covalently bound to a halogen. This electron deficiency results in an area of weak positive charge, on the halogen opposite to the covalent bond. It is this positive area, called the σ-hole, that attracts the electrons of the Lewis base, pulling them away from an electrophilic site, and causing it to react faster. The location of the σ-hole puts restrictions on the halogen bond such that the bond R—X···B, (R = electron withdrawing group, X = Halogen, B = Lewis base) must be 180°. Prof. Orion B. Berryman designed a family of catalysts that fulfills these requirements by placing two halogens on a scaffold that enables this geometry. The research highlighted herein is the synthesis of a catalyst derivative designed to enhance the catalyst solubility in organic solvents by incorporating tertiary-butyl groups on the structure. The synthesis involves subjecting 4-t-butylaniline through a five step process adding bromine and iodine to the ortho-positions and removes the amine by deamination. This dihalogenated species will then be attached to imidazole by a copper catalyzed N-arylation. Two of these arms will be attached to the meta-positions of a benzene ring by Suzuki-Miyaura cross couplings to create the back bone of the catalyst. Finally, both of the imidazoles will be iodinated and alkylated with MeOTf to activate the catalysts. Once the catalyst is synthesized, binding constants will be measured with carbonyl substrates and the catalyst will be tested with carbonyl reactions. Because these new organocatalysts are designed to be compatible with a large scope of substrates, especially carbonyl compounds, they could potentially improve known reactions and make new reactions possible.

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Apr 12th, 11:00 AM Apr 12th, 12:00 PM

Halogen Bonding

UC Ballroom

Halogen bonds are non-covalent attractive interactions between halogens that are covalently bound to organic structures, and Lewis bases (species with areas of high electron density). This attraction is caused by an electron-deficient group that is covalently bound to a halogen. This electron deficiency results in an area of weak positive charge, on the halogen opposite to the covalent bond. It is this positive area, called the σ-hole, that attracts the electrons of the Lewis base, pulling them away from an electrophilic site, and causing it to react faster. The location of the σ-hole puts restrictions on the halogen bond such that the bond R—X···B, (R = electron withdrawing group, X = Halogen, B = Lewis base) must be 180°. Prof. Orion B. Berryman designed a family of catalysts that fulfills these requirements by placing two halogens on a scaffold that enables this geometry. The research highlighted herein is the synthesis of a catalyst derivative designed to enhance the catalyst solubility in organic solvents by incorporating tertiary-butyl groups on the structure. The synthesis involves subjecting 4-t-butylaniline through a five step process adding bromine and iodine to the ortho-positions and removes the amine by deamination. This dihalogenated species will then be attached to imidazole by a copper catalyzed N-arylation. Two of these arms will be attached to the meta-positions of a benzene ring by Suzuki-Miyaura cross couplings to create the back bone of the catalyst. Finally, both of the imidazoles will be iodinated and alkylated with MeOTf to activate the catalysts. Once the catalyst is synthesized, binding constants will be measured with carbonyl substrates and the catalyst will be tested with carbonyl reactions. Because these new organocatalysts are designed to be compatible with a large scope of substrates, especially carbonyl compounds, they could potentially improve known reactions and make new reactions possible.