Conversion of Fusel Oil Alcohols to Alkyl Carbonates By Carbon Dioxide Fixation

The development of suitable methods for the preparation of interesting CO₂-containing compounds, like organic carbonates, is an alternative to recycling CO₂ and using it as a substitute for the highly toxic phosgene and its derivatives.^1–4 The selectivity and nature of the capture products are two of the most important aspects of the CO₂ fixation.^5,6 Organic carbonates can be synthesized by reaction of alcohols with CO₂ under catalytical conditions.^7,8 This process is relevant since both CO₂ and fusel oil are by-products from the sugar cane and ethanol production. Alkylcarbonates among other products have wide industrial applications, such as chemical,⁹ medicinal¹⁰ and fuel additives.¹¹ The present work describes the preparation of alkyl carbonates from reaction of fusel oil alcohols with carbon dioxide in the presence of 1.8-diazabicycloundecene (DBU) and 1.5-diazabicyclononene (DBN) and an alkylating agent. The capture of CO₂ by alcohols was carried out with nucleophilic activation of the isopentyl and isobutyl alcohols with the amidines DBU or DBN. The carbon dioxide fixation was accomplished by subsequent alkylation under pressurized-CO₂ conditions. The synthesis of butyl-isopentylcarbonate and butyl-isobtuylcarbonate were confirmed by FT-IR ana, lysis and GC-MS with EI ionization mode. In order to establish the conditions for better yields of the alkylcarbonates, it was investigated the influence of temperature, concentration of reagents, time of reaction and gas pressure in the synthesis.

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