Electrosynthesis of Bio-Based Dicarboxylic Acids

Abstract

Currently, oil and gas are dominating feedstocks for bulk and fine chemicals. However, limited fossil resources and growing awareness for the environment requires sustainable alternatives [1]. One potential source for renewable raw materials is wood. In the pulping process of wood to cellulose, large amounts of lignin and also turpentine accumulate as a by-product. With the holistic use of waste streams in mind, lignin and the components of the turpentine fraction represent promising sources for carbon building blocks. α-Pinene, the major compound of the turpentine fraction, can be oxidized to a biogenic dicarboxylic acid which finds a potential application as a hardener in bio-based thermosets. For a fully sustainable application, the necessity for renewable resources goes hand in hand with the demand for green chemical processes, such as electrosynthesis [2]. The key step of a possible oxidation sequence of α-pinene to bio-based dicarboxylic acids is successfully performed by electrocatalytical conversion of pinanediol to pinonic acid. To establish this transformation as a green method, we developed a simple, high-yielding protocol for the anodic oxidation of pinanediol, while maintaining of the intrinsic stereogenic information, at nickel oxidehydroxide anodes in water, the least hazardous of all solvents. [1] C. Brandt, Chem. Unserer Zeit 2002, 36, 214–224. [2] A. Frontana-Uribe, R. D. Little, J. G. Ibanez, A. Palma, R. Vasquez-Medrano, Green Chem. 2010, 12, 2099–2199. Figure 1