Grubbs's Cross Metathesis of Eugenol with cis-2-Butene-1,4-diol To Make a Natural Product. An Organometallic Experiment for the Undergraduate Lab

An experiment for the undergraduate organic laboratory course, the ruthenium catalyzed cross metathesis of eugenol with cis -1,4-butenediol, is described in detail. The Grubbs' catalyst is dispersed in paraffin wax to eliminate the need for inert atmosphere storage. Eugenol, the main component of clove oil, is coupled at room temperature overnight with cis -1,4-butenediol to yield the crystalline ( E )-4-(4-hydroxy-3-methoxyphenyl)but-2-en-ol, also a natural product. The experiment is an excellent example of the powerful selectivity possible with the Grubbs' catalyst. Both the preference for trans over cis alkene formation and for cross metathesis over homodimerization are demonstrated. The experiment also provides an opportunity for students to gain proficiency in the organic synthesis techniques of column chromatography, TLC, recrystallization, and melting point determination. Optional characterization of the product by IR, mass spec, and 1 H NMR make the experiment applicable for all levels of undergraduate organic students.