Organic carbonates: sustainable and environmentally-friendly ethylation, allylation, and benzylation reagents

Diallyl, dibenzyl, and diethyl carbonate are shown to be non-toxic, sustainable and efficient reagents for the alkylation of phenols as well as for an esterification of carboxylic acids under microwave irradiation in the presence of sub-stoichiometric quantities of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or potassium carbonate. Comparative studies with diethyl carbonate (DEC), diallyl carbonate (DAC), and dibenzyl carbonate (DBC) were performed for the etherification of phenol. Moreover, the reaction of these organic carbonates with hydrogenated ferulic acid show that ester formation is significantly faster and requires lower temperatures if compared to the etherification. Generally, DBC and DAC show a higher reactivity than DEC. Moreover, the use of DBC and DAC under optimized reaction conditions allowed a selective protection of carboxyl groups in the presence of phenols.