| 초록 |
The hydroformylation of α,β-unsaturated esters is an attractive synthetic route for the preparation of 1,3-and 1,4-difunctional compounds, which can subsequently be converted to malonic acid derivatives and γ-butyrolactones. Numerous neutral and cationic rhodium compounds have been investigated as catalysts, and recently the zwitterionic rhodium compound, Rh(cod)(η6-PhBPh3), has been shown to be an excellent precatalyst for the reaction. The regiochemistry of the reaction strongly depends on the catalyst system and the substrates employed. An investigation was made of the effect of 1,4-bis(diphenylphosphino)butane (dppb) on the regioselectivity of the hydroformylation of α,β-unsaturated esters with synthesis gas, catalyzed by rhodium(Ⅰ) complexes. Excellent α-selectivity occurs when dppb is added as a ligand in the hydroformylation of α,β-unsaturated esters catalyzed by rhodium(Ⅰ) complexes. When methyl acrylate and α-methylene-γ-butyrolactone are used as substrates, dppb significantly promotes the hydroformylation. However, dppb inhibits the reaction when methyl methacrylate is used as the substrate. In the absence of dppb, the hydromylation of methyl methacrylate catalyzed by Rh(cod)(η6-PhBPh3) shows increasing β-selectivity with increasing temperature.
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