Final Abstract for URS Program
The aim of this research project is to expand the scope of 4 + 3 cycloadduct chemistry by varying functional groups attached to the prerequisite oxidopyridinium ion for each respective cycloadduct product. While N-substitution of the pyridinium precursor is known to proceed smoothly if alkylated by a lone methyl group, we evaluated the effect a larger alkyl group would have on the overall yield of the 4 + 3 cycloadduct product.
Isobutyl triflate, generated from the known reaction between isobutyl alcohol and triflic anhydride, was reacted with ethyl 5-hydroxy-nicotinate to generate the respective N-isobutyl oxidopyridinium ion in quantitative yield, which subsequently underwent a 4 + 3 cycloaddition reaction with 2,3-dimethylbutadiene to generate the desired 4 + 3 cycloadduct in 67% yield. Furthermore, we experimented with N-acyl substitution of the oxidopyridinium ion in 4 + 3 cycloaddition reactions. (Trans)-2-phenylcyclohexyl 2-chloroacetate, derived from (trans)-2-phenylcyclohexanol, and chloroacetyl chloride using a known literature procedure, were reacted with ethyl 5-hydroxy-nicotinate to generate the respective N-acyl oxidopyridinium ion in quantitative yield, which subsequently underwent a 4 + 3 cycloaddition reaction with 2,3-diemethylbutadiene to generate the desired 4 + 3 cycloadduct in 28% yield.
While we were able to cleanly obtain the desired 4 + 3 cycloadduct products for each derivative, reaction condition modifications are necessary to improve the overall yields for each new compound. Future research could include modifying the conditions of the aforementioned reactions to achieve better results and running these reactions with different substituents to obtain new derivatives of the (4+3) cycloadduct product.