Synthesis of Cyclic Carbonates from Propargylic Alcohols

Synthesis of Cyclic Carbonates from Propargylic Alcohols 

Cyclic carbonates have also been synthesized from propargylic alcohol derivatives and C02 as the starting materials. This synthetic approach (Equation 7.22) is based on cyclization of the propargylic carbonate moiety (HC=CCH20C02-) into the corresponding a-alkylidene CC, in the presence of a suitable catalyst such as ruthenium [202], cobalt [203], palladium [204, 205], copper [206-211], or phosphine [212-214], 

The reaction usually proceeds in volatile organic solvents, such as DMF or THF, and requires large amounts of organic solvents, and a high C02 pressure (ca. 5.0MPa). 

Recently, Ikarya has reported the use of imidazolin-2-ylidenes with N-alkyl and N-aryl substituents and their C02 adducts as catalyst of the carboxylative cydiza-tion of internal and terminal propargylic alcohols [215], The reaction of internal propargyl alcohols with C02 has been carried out also under supercritical conditions. Ikariya et al. have developed a synthetic process to afford Z-alkylidene cyclic carbonates promoted by P( -C4H9)3 with high efficiency [216], 

An IL (l-butyl-3-meffiylimidazolium benzene sulfonate [BMIm][PhS03]) has also been used as a reaction medium for the synthesis of a-methylene CCs from C02 and propargyl alcohols, using transition metal salts as the catalyst (Equation 7.23) [217]. 

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