**2. Biobased ionic liquids**

Due to their biodegradability and non-toxicity, the use of renewable resources could improve the green character of ILs. Among biobased precursors, building blocks such as amino acids [15] and amino alcohols from proteins, sugars from cellulose, chitin, starch and other polysaccharides, aromatic aldehydes from lignin and other compounds like fatty acids from vegetable or algae-derived oils can be used.

Amino acids or esters have been commonly used for the preparation of cations through classical acidification reaction or esterification/anionic metathesis sequences [16, 17]. The syntheses of all these ILs are summarised in **Scheme 1**. Protic or aprotics ILs could also be prepared, but their stability under acidic conditions was not suitable. One interesting example of such IL was presented by Trivedi et al. in which the counter anion was a sodium lauryl sulphate [18].

*N*-Heterocyclic amino acid-derived [19] chiral imidazolium based on valine, leucine and alanine [20], 4,5-dihydrothiazolium derived from biobased amino alcohol [21] and chiral pyrrolidine-based ILs from proline [22, 23] have been also prepared by synthetic ways involving more than four reaction steps. Gathergood et al. proposed some ILs with a neutral amino acid side chain that showed improvement on biodegradability [24]; they described also very recently L-phenylalanine ethyl ester ILs and non-ionic derivatives [25], and a series of amino acid derived ionic liquids showing microbial toxicity and biodegradation [26]. In addition, one of these last ILs presented the advantage to have antimicrobial properties. Betaine or betaine derivatives (**Scheme 2**) could be also transformed into ionic liquids, which can be used in extraction processes [27] or as herbicidal compounds [28]. Recently, de Almeida Meirelles et al. reviewed the use of ILs for food and bioproducts Industries; the authors suggested that biobased ILs could be use in food processes, especially when derived from amino acids or choline, and that moreover, their biocompatibility could even improve the methods [29].

**Scheme 1.** Examples of aminoacids or esters-based as cations for ILs.

intensively investigated for the last three decades as green alternatives to conventional organic solvents [6–8]. Indeed, their numerous properties confer to these compounds the opportunity to replace classical organic solvents and their fields of applications are numerous: electrochemistry, organic synthesis, catalysis, complexation, extraction, etc. [4]. However, their low biodegradability or the toxicity of their degradation products and their high (eco)toxicity led the scientific community to reduce their use or to find other greener alternatives [9–13]. Considering this aspect, biobased ionic liquids could be a good alternative to classical ionic

This chapter will be dedicated to the description of hydrogenation procedures of (poly) alkenes or unsaturated ketones in biobased ionic liquids (ILs). In order to present this specific topic, the first part of the chapter will present the preparation of various biobased ionic liquids. Next, general procedures of hydrogenation in "classical" ILs will be developed according to recently published reviews. Finally, we will show that hydrogenation processes could be

Due to their biodegradability and non-toxicity, the use of renewable resources could improve the green character of ILs. Among biobased precursors, building blocks such as amino acids [15] and amino alcohols from proteins, sugars from cellulose, chitin, starch and other polysaccharides, aromatic aldehydes from lignin and other compounds like fatty acids from

Amino acids or esters have been commonly used for the preparation of cations through classical acidification reaction or esterification/anionic metathesis sequences [16, 17]. The syntheses of all these ILs are summarised in **Scheme 1**. Protic or aprotics ILs could also be prepared, but their stability under acidic conditions was not suitable. One interesting example of such IL was presented by Trivedi et al. in which the counter anion was a sodium lauryl

*N*-Heterocyclic amino acid-derived [19] chiral imidazolium based on valine, leucine and alanine [20], 4,5-dihydrothiazolium derived from biobased amino alcohol [21] and chiral pyrrolidine-based ILs from proline [22, 23] have been also prepared by synthetic ways involving more than four reaction steps. Gathergood et al. proposed some ILs with a neutral amino acid side chain that showed improvement on biodegradability [24]; they described also very recently L-phenylalanine ethyl ester ILs and non-ionic derivatives [25], and a series of amino acid derived ionic liquids showing microbial toxicity and biodegradation [26]. In addition, one of these last ILs presented the advantage to have antimicrobial properties. Betaine or betaine derivatives (**Scheme 2**) could be also transformed into ionic liquids, which can be used in extraction processes [27] or as herbicidal compounds [28]. Recently, de Almeida Meirelles et al. reviewed the use of ILs for food and bioproducts Industries; the authors suggested that biobased ILs could be use in food processes, especially when derived from

liquids but their preparation remains relative long and costly [14].

308 New Advances in Hydrogenation Processes - Fundamentals and Applications

performed in biobased ILs with few examples.

vegetable or algae-derived oils can be used.

**2. Biobased ionic liquids**

sulphate [18].

**Scheme 2.** Examples of aminoacids or esters-based as anions for ILs.

Aminoacids could as well be used to build the anionic part of the ILs. They are commonly associated with imidazolium, ammonium or phosphonium cations (**Scheme 2**) [30, 31].

In our group, an acido-basic method was used to form various ILs with anion from natural acids (L-lactic, L-tartaric, pyruvic, malic, malonic, succinic and osidic acids), but also L-proline and its derivatives. Even they were not readily biodegradable, these compounds showed in general lower toxicity towards various organisms than usual chlorinated and commercial ILs (**Scheme 3**) [32].

**Scheme 3.** Biomass-derived acid-based ILs.

Concerning the sugar family, these starting materials were essentially used to build cations. Fructose [33], glucose [34, 35], arabinose [36], isomannide [37] or isosorbide [38] have been transformed through multistep reactionnal pathways (**Scheme 4**). The resulting ILs were mainly used as chiral agents and presented in general low decomposition temperatures.

**Scheme 4.** Examples of sugar-based ILs.

Our group developed particularly xylose-derived ILs wearing a triazolium group. They were obtained by click chemistry between alcynated xylose and azido alkyls or benzyl, followed by methylation [39] (**Scheme 5**). Positive glass transition and low decomposition temperatures were observed, which seemed to be in relation with the presence of sugar moieties. Considering these temperatures, these ILs could only be used under mild conditions as solvents or chiral agents for chemical transformations or catalysis.

**Scheme 5.** Xylose-derived ILs.

In our group, an acido-basic method was used to form various ILs with anion from natural acids (L-lactic, L-tartaric, pyruvic, malic, malonic, succinic and osidic acids), but also L-proline and its derivatives. Even they were not readily biodegradable, these compounds showed in general lower toxicity towards various organisms than usual chlorinated and commercial ILs

Concerning the sugar family, these starting materials were essentially used to build cations. Fructose [33], glucose [34, 35], arabinose [36], isomannide [37] or isosorbide [38] have been transformed through multistep reactionnal pathways (**Scheme 4**). The resulting ILs were mainly used as chiral agents and presented in general low decomposition temperatures.

(**Scheme 3**) [32].

**Scheme 3.** Biomass-derived acid-based ILs.

310 New Advances in Hydrogenation Processes - Fundamentals and Applications

**Scheme 4.** Examples of sugar-based ILs.

Lipids represent also biosourced compounds, which could generate both cations and anions for ILs. Even if imidazolium-wearing oleic and stearic chain were easily prepared [40], the major utilisation of these lipids concerned the formation of anions, which were next associated with ammonium or phosphonium cations (**Figure 1**) [41].

**Figure 1.** Lipids-based ILs.

Hulsbosch et al. described more exotic examples of bioresources for ILs as ephedrine or ampicillin in a recent and quite complete review dedicated to biobased ionic liquids for industry processing (**Scheme 6**) [14].

**Scheme 6.** Ephedrine- or ampicillin-based ILs.
