Tin triflate-catalyzed conversion of cellulose to valuable (α-hydroxy-) esters

• DOI: 10.1016/j.cattod.2016.01.035
• Publication Date: 2016-02-16T11:33:01Z
• Authors: Michiel Dusselier; Rik De Clercq; Roy Cornelis; Bert F. Sels
• Keywords: 01 natural sciences; 0104 chemical sciences

Abstract The direct conversion of cellulose with metal-triflate catalysts in methanol is investigated. Sn II -triflate remarkably catalyzes the formation of a mixture of useful α-hydroxy esters such as methyl lactate, methyl vinyl glycolate and methyl-4-methoxy-2-hydroxybutanoate, on top of methyl levulinate. Compared to other metal triflates or Sn salts, the catalytic features of Sn II -triflate are distinct and linked to the interplay between its Bronsted and Lewis acidic component. A total ester yield (carbon-based, mol%) in the 60%-range could be obtained from cellulose after 2 h at 200 °C for cellulose loadings up to 20 g L −1 with 4.8 mM of catalyst. The cascade reaction network, confirmed by feeding intermediates, highlights the importance of a fast retro-aldol of the hexose intermediates – opposed to their dehydration – when α-hydroxy esters are targeted. By manipulating the triflate-to-Sn ratio, nearly 40% of α-hydroxy esters can be produced in a one-pot approach. Such mixtures could help fuel the demand for functional biodegradable polyesters.