Synthesis of a biofuel target through conventional organic chemistry

Abstract

In this work, the biofuel target compound 2-ethyl-5,5-dimethylcyclopenta-1,3-diene (1) and its exo isomers (9a and 9b), were successfully synthesized via two different pathways from the common intermediate 4,4-dimethylcyclopent-2-ene-1-one (2). The first pathway produced the endocyclic product as a pure isomer via a triflate intermediate obtained from ketone 2 in 60% yield, followed by copper-catalyzed coupling with ethyl magnesium bromide in 63% yield. The second pathway employed a Grignard reaction with ketone 2, which generated an alcohol that was immediately subjected to mild acid-catalyzed elimination to yield primarily a mixture of exo isomers 9a and 9b in 46% yield. The preparation method developed by this work allowed for the production of a sufficient quantity of these targets to evaluate their fuel properties, which will be reported in a separate study.