Carbohydrates compounds from renewable

Ethyl lactate is a nontoxic and biodegradable solvent derived from renewable carbohydrates. Its use and acceptance can be increased only if it is competitively priced to replace traditional organic solvents such as methylene chloride and chloroform. Argoime s National Lab developed a selective membrane technology for synthesizing ethyl lactate that eliminates the production of an equimolar amount of salt waste. The process uses pervaporation membranes and catalysts to directly convert the salts to esters, thereby eliminating the problem of salt waste. This approach reduces the product cost by half. The concept of pervaporation consists of the use of a membrane that selectively accepts one compound from a mixture of compounds it is explained in Chapter 6. 

Propylene oxide is one of the top 50 chemicals. More than 4 million t/a are produced worldwide. It is reacted via polyetherpolyols to form polyurethanes and via propylene glycol to form polyesters 15). Obviously, the polyol and diol functionalities are used to form with diisocyanates derived from diamino compounds polyurethanes and with diacids polyesters, respectively. These functionalities are available from renewable feedstocks carbohydrates, oils and fats, proteins and lignins. 

Consideration of renewable feedstocks as petrochemical substitutes also leads one immediately to the problem of manipulating oxidation levels, but in a different sense. Carbohydrates are die most common primary class of compounds available from renewable biomass (S), yet these compounds are... 

It is worth pointing out that, besides o-sorbitol 19 and D-mannitol 36, other low-molecular weight building blocks have been already obtained on the ton-scale from low cost or waste polymeric carbohydrates (starch, cellulose, hemicellulose, chitin) [80, 81]. Most of these compounds are densely functionalized enantiopure molecules that can be easily converted into high-value added products, including chiral ionic liquids. Therefore, further studies are required to develop other synthetic approaches to environmentally sustainable ionic liquids based on renewable raw materials. 

Some other natural compounds have been transformed for their use in the synthesis of polymers via olefin metathesis processes. As mentioned in the introduction, furans, which are obtained from carbohydrates, are perfect precursors of monomers for ROMP via simple Diels-Alder cycloadditions (n) (Scheme 25) [26]. In this regard, the first example of the ROMP of 7-oxabicyclo[2.2.1]hept-5-ene derivatives was reported by Novak and Grubbs in 1988 using ruthenium- and osmium-based catalysts [186]. The number of examples of ROMP with monomers with this generic structure is vast, and it is out of the scope of this chapter to cover all of them. However, it is worth mentioning here the great potential of a renewable platform chemical like furan (and derived compounds), which gives access to such a variety of monomers. 

This book is a volume in the series Topics in Heterocyclic Chemistry. It covers the key methods used for designing synthetic approaches to heterocycles from carbohydrates and the value and scope of these methods. Carbohydrates are widely distributed in nature and constitute the largest part of renewable biomasses. Moreover, many carbohydrates and their derivatives are commercially available at relatively cheap prices. Consequently their utiUzation is highly encouraged and economically they are of great significance. Moreover, carbohydrates are highly functionahzed compounds that can be readily deriva-tized and/or cyclized to provide heterocychc compounds. 

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