Organic synthesis is an important scientific research activity that creates new molecules that have desirable properties, for instance as medicines or materials (molded plastics, bullet proof vests, medical devices, etc.). However, organic synthesis is inherently wasteful because many other chemicals are needed to make the desired molecules often through many steps (multistep synthesis). When these other chemicals are used they are called reagents and their use leads to byproducts which become a chemical wastestream, which must be disposed. A field of organometallic chemistry called catalysis seeks to create new catalysts and to design new catalysts that are tailored to perform a specific function without all the waste of using additional reagents and generating waste. Greater efficiency leads to cheaper processes to make medicines, to make alternative fuels and to obtain cheaper material products. In addition to forming new bonds, catalysis aims to control how atoms are positioned in space, called stereoselectivity. Currently, the olefin metathesis provides one of the most effective methods for catalytic carbon-carbon double bond construction, and has been widely used by chemists in many fields. Despite the huge success of metathesis chemistry, the major limitation is control of double bond geometry. This NSF-sponsored research project CHE0848560 focused on synthesizing a group of ruthenium carbene catalysts with a new design in order to improve the selectivity for alkene and ene-yne metathesis. Catalysts were designed and synthesized with groups aligned on one side of the molecule to influence the stereoselectivity. Though the catalysts proved reactive, their structural modifications were not significant enough and did not dramatically improve the stereoselectivity. Another limitation of catalysis, that of excess reagents, was addressed in applications of a reaction called ene-yne metathesis. A new reaction was created to use less reagent which not only improved the economy of the reaction but also achieved a high level of selectivity. Further applications improved the synthetic scope of the reaction by using a new approach to make unreactive alkenes react. Overall, this project led to new ruthenium carbene catalysts able to catalyze alkene and ene-yne metathesis, led to a number of published papers giving our results and made the ene-yne reaction more efficient and applicable to a wider scope of substrates. The project also illustrated that incremental approaches to catalyst modification were too minute to have a major effect on selectivity. This research project led to new insight into the reaction and the factors that control selectivity. 

Last Modified: 10/02/2012
Modified by: Steven T Diver