FT Raman--a valuable tool for surveying kinetics in RCM of functionalized dienes

In this article the suitability of FT Raman spectroscopy for monitoring kinetics of ring-closing metathesis promoted by the Grubbs' 1st generation precatalyst was demonstrated for the first time. Reactions at room temperature and under low catalyst loadings were carried out on a series of representative diene substrates. The time evolution of the characteristic Raman stretching vibrations unequivocally described the reaction progress allowing for precise calculation of the substrate conversion and of the yield in the expected cyclic product, based on the corresponding peak heights. The responsive Raman technique demonstrated clean RCM pathways for diethyl diallylmalonate and diallyl ether whereas a minor olefinic side-product was detected in the case of diallyl phthalate. The study provides essential underpinnings for future utilization of Raman spectroscopy, concurrently with NMR or supplementing it, for the evaluation of RCM reactions.