Olefin Metathesis in Green Organic Solvents and without Solvent
Résumé
This chapter focuses on olefin metathesis transformations in green(er) organic solvents, including supercritical carbon dioxide (scCO2) and organic carbonates, in particular dimethyl carbonate (DMC) and poly(ethylene glycol) (PEG). It reviews the domain of a solvent very often quoted as the greenest or best solvent in green chemistry textbooks, namely, no solvent or solventless conditions. DCM is often used in ruthenium-catalyzed metathesis reactions as it is in general a good catalyst solvent. Recently, ring closing metathesis (RCM) of diethyl diallylmalonate (DEDAM) and cross metathesis of allylbenzene with cis-1,4-diacetoxy-2-butene were studied, both under solvent-free conditions and in methyl decanoate, a renewable and environmentally benign solvent derived from fatty acid derivatives. More recently, the synthesis of nitrogen containing heterocycles by ruthenium catalyzed RCM using low catalyst loading was studied by Grubbs.