In the use of CO2 and CO2-based compounds as feedstocks, dialkyl carbonates (DACs) and in particular dimethyl carbonate (DMC) occupy a privileged position due to their low toxicity, high biodegradability and peculiar reactivity.
Nowadays, the large-scale production of DACs is carried out through clean processes (i.e., phosgene-free processes), which includes the direct insertion of CO2 into epoxides, allowing – in principle – recycling of the carbon dioxide emitted during carbonate degradation. This prevents pollution at the source.
DACs are ambident electrophiles, which under appropriate conditions can undergo BAc2- or BAl2-nucleophilic substitutions to give, respectively, alkoxycarbonylation and alkylation reactions. The reactivity of DMC is tunable: at 90 °C, methoxycarbonylations take place, whereas at higher reaction temperatures methylation reactions are observed with a variety of nucleophiles. In the particular case of substrates susceptible to multiple alkylations (e.g., CH2-active compounds and primary amines), DMC allows unprecedented selectivity toward mono-C- and mono-N-methylation reactions with a chemoselectivity up to 99%.
Moreover, DMC-mediated methylations are truly catalytic reactions that use safe solids (alkaline carbonates or zeolites), thereby avoiding the formation of undesirable inorganic salts as byproducts.
This groundbreaking achievement has definitely drawn attention toward the conception of procedures to activate the rather stable DACs with the aim of employing these compounds as green alternatives to their reactive chlorinated analogues.
This seminar reports also on DACs as alkoxycarbonylating agents and their applications in industry and fine synthesis, as well as alkylating agents including allylic alkylation using palladium catalysts and anchimerically driven alkylations via mustard carbonates analogues.
The reactivity of organic carbonates toward several substrates and under different reaction conditions is described along with some distinctive DAC-mediated cyclization and transposition reactions which can be carried out under continuous-flow conditions.
The many efforts devoted to improving the industrial suitability of organic carbonates have unveiled an intriguing and innovative chemistry as demonstrated by the numerous publications and patents published on these compounds over the last thirty years.
Professor of Organic Chemistry; retired on 2016, he is responsible of scientific projects on Green Chemistry at Ca’ Foscari University of Venice and Coordinator of UNESCO-UNITWIN "Green Chemistry Excellence from Baltic Sea to Mediterranean Sea and Beyond".
He was guest researcher and teacher at College Station (Texas,1979-1981), Potsdam (New York, 1989-90) and Syracuse (New York, 1991-92), Chapel Hill, (North Carolina, 1995).
He is Member of the Bureau of IUPAC and Chair of IUPAC Interdivisional Committee on Green Chemistry for Sustainable Development.
P: Tundo is author of about 350 scientific publications, 40 patents and many books.
His scientific interests are in the field of organic synthesis in selective methylations with low environmental impact, continuous flow chemistry, chemical detoxification of contaminants, hydrodehalogenation under multiphase conditions, phase-transfer catalysis (gas-liquid phase-transfer catalysis, GL-PTC), synthesis of crown-ethers and functionalized cryptands, supramolecular chemistry, heteropolyacids, safe alternatives to harmful chemicals and finally Green Chemistry for Cultural Heritage.
He is the sole author of the book “Continuous flow methods in organic synthesis” E. Horwood Pub., Chichester, UK, 1991 (378 pp.), and editor of about 20 books.
P. Tundo was President of Organic and Biomolecular Chemistry Division of IUPAC (biennium 2007-2009) and holder of the Unesco Chair on Green Chemistry (UNTWIN N.o 731). He founded and was Chairman (2004-2016) of the Working Party on “Green and Sustainable Chemistry” of EuCheMS (European Association for Chemical and Molecular Sciences).
Founder of the IUPAC International Conferences Series on Green Chemistry, he was awarded by American Chemical Society on 1983 (Kendall Award, with Janos Fendler), and by Federchimica (Italian association of chemical industries) on 1997 (An Intelligent Future).
P. Tundo coordinated many institutional and industrial research projects (EU, NATO, Dow, ICI, Roquette) and was the founder and the Director of the 10 editions of the annual Summer Schools on Green Chemistry (Venezia, Italy) sponsored by the EU, UNESCO and NATO.