Sustainable valorisation of renewables through dialkyl carbonates and isopropenyl esters

Abstract

This review showcases a thorough analysis of reactions and applications of the most widespread linear and alkylene organic carbonates (DACs), dimethyl-, diethyl-, ethylene-, and propylene-carbonates (DMC, DEC, EC, and PC, respectively), and a representative enol ester isopropenyl acetate (iPAc), for the chemical functionalisation and upgrading of renewable compounds, including both bio-based platform molecules and biopolymers. The work, which follows a previous survey published by us in 2018 and limited to DMC only, is organised into five sections where the literature screening encompasses the past 4 years in the case of DMC and a wider timespan of 5–6 years for other homologues/analogues carbonates and iPAc. After a general introductory section on benign-by-design processes for the conversion of biomass derivatives, a description of synthetic methods of DACs follows. Most of the review content is then focused on reactions in which DACs and iPAc act as alkylating, carboxylating, and acylating agents, respectively, and processes where the same compounds are used as solvents. Topics are grouped starting from the valorisation of small renewable molecules such as glycerol, cyclic carbonates, carbonyl derivatives of furfural and HMF, then proceeding with bio-monomers, and ending up with the synthesis and functionalisation of biopolymers. The investigated examples have been detailed by providing conditions and scope, the proposed reaction mechanisms when available, and a rationale behind the choice of reaction/process parameters (T, p, catalyst(s), etc.). Criticism and comments have been put forward on the pros and cons of the described methods and their perspectives, as well as on those studies which still require follow-ups and more in-depth analyses.