Abstract
A new regioselective approach has been elaborated for the selective conversion of bio-based glycerol into the monomethyl derivative using sub/supercritical methanol. The reaction was realized in a batch process using three reactive components, namely, glycerol, methanol, and potassium carbonate to selectively produce the 3-methoxypropan-1,2-diol in mild yields; the mechanism of the O-methylation has been delineated using labeled methanol and GC-MS experiments.
Highlights
To compensate for the constantly diminishing fossil-derived resources, the concept of biorefinery and the use of vegetable oils has emerged as a promising alternative to meet future challenges in both public and industrial sectors (Biermann et al, 2000; Behr et al, 2008)
To improve the regio- and stereoselectivity starting from glycerol, protection–deprotection steps using solketal (Vanlaldinpuia and Bez, 2011; Jiang et al, 2013; Jakubowska et al, 2015), as well as activation steps deploying glycidol (Cucciniello et al, 2016; Leal-Duaso et al, 2017; Ricciardi et al, 2017, 2018), were necessary to produce the target glycerol ethers, which limits the interest in view of the cost and sustainability
In order to provide a greener protocol for the selective etherification of glycerol, we disclose a novel O-methylation of glycerol (1) into the corresponding 3-methoxypropan-1,2-diol and (2) in the presence of a common and widely available homogeneous base under subcritical methanol
Summary
To compensate for the constantly diminishing fossil-derived resources, the concept of biorefinery and the use of vegetable oils has emerged as a promising alternative to meet future challenges in both public and industrial sectors (Biermann et al, 2000; Behr et al, 2008). MAGEs bearing short O-alkyl chains have an impact on the energy sector as exemplified by the good fuel additive properties of 3-methoxypropan-1,2-diol (2) (Chang et al, 2012). Starting from glycerol (1), the direct one-step synthesis of glycerol ethers has been reported using different conventional methods: the Williamson-type synthesis, catalytic O-telomerization, acid catalysis, and reductive alkylation (Sutter et al, 2012), among others. Acid homogeneous and heterogeneous catalysts such as Bi(OTf) (Liu et al, 2013), Amberlyst-15 (Pariente et al, 2009), and silica-supported sulfonic groups (Gu et al, 2008) have been used, with success, for the synthesis of MAGEs. Among the documented research on direct MAGE synthesis, the use of critical alcohol as a solvent and reagent in the presence of homogeneous bases has not been described. In order to provide a greener protocol for the selective etherification of glycerol, we disclose a novel O-methylation of glycerol (1) into the corresponding 3-methoxypropan-1,2-diol and (2) in the presence of a common and widely available homogeneous base under subcritical methanol
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