Session VII

Wednesday, May 24th

Session VII


T33

"Copper-Catalyzed Enantioselective Carboetherification and Hydroetherification

of Unactivated Alkenes to form Cyclic Ethers"

Ilyas Berhane and Sherry R. Chemler

University at Buffalo, Department of Chemistry

Chiral six and seven-membered saturated oxygen heterocycles are present in a variety of natural products and make up the core of many bioactive compounds. Thus, there is a need to develop tools to synthesize them efficiently and enantioselectively. The stereoselective metal-catalyzed cyclization of an alcohol across an alkene is a direct approach to form a functionalized saturated oxygen heterocycle. Herein, we describe the first enantioselective copper-catalyzed carboetherification and hydroetherification of unactivated alkenes to make six-membered cyclic ethers. Aspects related to reaction scope, mechanism, and synthetic application will be presented. 

T34

Size-Selective Organocatalysis using Macrocycle N-Heterocyclic Carbene

Yutong Zhang, Anibal Davalos and Steven T. Diver

University at Buffalo, Department of Chemistry

N-Heterocyclic carbenes (NHCs) are highly versatile as both nucleophilic catalysts and supporting ligands for most transition metals. However, they do not display selectivity when substrates have small changes in molecular structure. Our synthesis of new catalysts where the NHC resides inside a macrocycle ring will be described. The defined size of the cavity was expected to provide size selectivity in a range of catalytic applications. Our investigation started with the intramolecular Michael-Stetter reaction, which is a powerful method for construction of carbocyclic and heterocyclic rings. Interestingly, our studies have shown that the macrocyclic NHCs were able to distinguish between small variations in substrate structure remote from the reactive site. Our recent effort of synthesizing Ruthenium-NHC complex will also be described.

T35

Copper-Catalyzed Three Component Intermolecular Carboamination of Alkenes Utilizing Potassium Alkyl Trifluoroborate Salts

Erik Boldt, and Sherry R. Chemler

University at Buffalo, Department of Chemistry

Metal catalyzed alkene difunctionalizations are highly useful transformations in synthetic chemistry. However, constructing carbon-carbon and carbon-nitrogen bonds in a single step still proves to be a challenging problem. Many current carboamination reactions require a tethered amine to create the C-N bond intramolecularly, which limits their scope.  Developing an efficient intermolecular carboamination reaction would be beneficial. Herein we describe a copper-catalyzed intermolecular carboamination using alkyl trifluoroborates as carbon radical sources.

T36

Synthesis and Interfacial Assembly of Multicomponent Bottlebrush Copolymers

Maryam Mazloumi and Javid Rzayev

University at Buffalo, Department of Chemistry

Polymeric materials with nanosized channels can serve as versatile platforms for a variety of applications. Self-assembly of block copolymers into nanostructured morphologies and subsequent removal of one of the components provides a reliable route to nanoporous polymers with high pore densities and controlled pore sizes. However, this approach is hindered by difficult control of morphology orientation and a limited pore size range. In this work, we develop multicomponent bottlebrush copolymers that generate nanoporous membranes with highly aligned channels and controlled pore sizes upon interfacial self-assembly. Bottlebrush copolymers are macromolecules with a highly branched architecture containing polymeric side chains on each repeat unit. Steric repulsion between densely grafted polymeric side chains causes the backbone to stretch out, giving rise to macromolecules with persistent cylindrical shapes in solution. The target bottlebrush copolymers were designed to contain core-shell hydrophobic domains with a cross-linkable shell layer and degradable core layer to generate nanoporous structures, as well as a hydrophilic block to aid in interfacial assembly and vertical alignment of the molecules at the interface. The polymers were synthesized by ring-opening metathesis of the corresponding macromonomers, which were prepared by a combination of controlled radical and ring opening polymerizations. The assembly of these macromolecules at the air/water interfaces will be pursued as a way to generate highly aligned nanoporous membranes with pore sizes < 10 nm, difficult to achieve by traditional block copolymer assembly methods.