4-Methoxycarbonyloxy-2-butyn

A novel synthetic method for the cyclic carbonates 85 was reported by Ihara et al. (Scheme 26) [66-68]. The reaction of 4-methoxycarbonyloxy-2-butyn-l-ol 83 with phenols 84 in the presence of Pd2(dba)3.CHCl3 and dppe gave 85 in good yields. Firstly, the generation of the allenylpalladium 86 would take place which is then attacked by ArOH 84 to produce the 7r-allylpalladium complex 87, which undergoes insertion of CO2 to give 85. Thus, recyclable use of CO2 molecule is possible in this reaction. 

M. Yoshida, M. Fujita, T. Ishii, M. Ihara, A novel methodology for the synthesis of cyclic carbonates based on the palladium-catalyzed cascade reaction of 4-methoxycarbonyloxy-2-butyn-l-ols with phenols, involving a novel carbon dioxide elimination-fixation process, J. Am. Chem. Soc. 125 (2003) 4874-4881. 

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