Diethyl Mesoxalate, A Representative Tricarbonyl Compound – A Useful Synthetic Tool Possessing Diverse Reactivities

Diethyl mesoxalate, a vicinal tricarbonyl compound, possesses multiple functionalities that facilitate diverse chemical conversions. The central carbonyl group with two ester functionalities exhibits high electrophilicity to accept nucleophilic attacks of various reagents. This unusual electrophilicity enables the reaction with acid amides that are not common nucleophiles in organic syntheses. Condensation with active methylene compounds or amines leads to electron‐deficient alkenes and imines, respectively, which can be transformed into more complex polyfunctionalized compounds by a second nucleophilic addition. Chemical transformations between the central and adjacent ester carbonyls furnish new ring systems that are useful in material and pharmaceutical sciences. The central carbonyl group can also be built into a ring system by reacting with reagents possessing nucleophilic and electrophilic sites. Furthermore, the central carbonyl serves as a dienophile that undergoes cycloaddition to form functionalized heterocyclic compounds in a single step. Diethyl mesoxalate (DEMO) is a highly useful synthetic reagent to exhibit diverse reactivities because of the high electrophilicity and multiple functionalities, The bulkiness of DEMO enables the stereo control to realize enantioselective/diastereoselective reactions. It is also possible to accelerate Diels–Alder reactions by chelation of the ester carbonyls.