Studies into the synthesis of alkyne dienophiles with n6 - Ruthenium Arene Complex Substituents

Abstract

In organic chemistry, ?6-metal arene complexes constitute a class of valuable intermediates in organic synthesis due to the metals ability to act as a strong electron withdrawing group.1-9 While known for being an electron withdrawing group, little research regarding their ability to accelerate the Diels-Alder (DA) reaction - which is known to be accelerated by electron-withdrawing dienophile substituents -has been done. Previous work by the Hitt research group has strongly suggested that the DA reaction can be accelerated by an alkene dienophile with a ?6 -ruthenium arene substituent.10 However, the effects of using an alkyne dienophile with a ?6 -ruthenium arene substituent have not been explored. Herein we report the synthesis of model dienophile precursor 3-phenyl-2-propenoic acid ethyl ester via an acyl substitution reaction. We also report our three attempts at synthesizing the alkyne dienophile [CpRu(?6-(3-phenyl-2-propenoic acid ethyl ester ))]PF6 . Unfortunately, after these three attempts, no product was obtained. It was thought that the alkyne in 3-phenyl-2-propenoic acid ethyl ester acted is a strong ligand to the CpRu+ moiety thus inhibiting complexation to the aryl ring.