2-formylpropanoate ester

As reported above, a literature survey shows that the hydroformylation of this class of alkene has been scarcely investigated. Indeed, these studies have been devoted exclusively to the hydroformylation of arylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethoxyethyl acrylate, and 2-ethylhexyl acrylate (Eq. 4) [18-21], Most attention has been focused on the hydroformylation of methyl acrylate to 2-formylpropanoate ester since the latter is used extensively for the synthesis of pharmaceuticals and may also be considered as a potential source of methyl methacrylate [18]. 

The hydroformylation of a,p-imsaturated esters by SAPC has also been investigated [34]. Several 2-formylpropanoate esters, which are widely used as intermediates in the synthesis of pharmaceuticals like rifamycin and vitamin E, were obtained using the water-soluble complexes. There are huge prospects for SAPC in the hydroformylation reaction for obtaining molecules having a broad-spectrum therapeutic activity. 

In this case, the best results are achieved with the yeast Saccharomyces rouxii130. Ethyl 2-formyl-alkanoates are reduced by baker s yeast in good yields but only moderate ee, e.g., ethyl 2-formylpropanoate is reduced to the (/ )-configurated hydroxy ester in 70 - 80% chemical yield and 60-65% ee131. 

Various a-formyl esters can be generated from the hydroformylation of a,P-unsaturated esters and diesters. Ethyl 2-formylpropanoate 33 can be obtained from the hydroformylation of ethyl acrylate 32. The reaction was catalyzed by the Rh2Cl2(CO)2/phosphine/NEt3 system at 20-40 °C in the presence of H2/CO (1/1, 20 atm), and yielded the product with excellent regioselectivity (98-100%). Particularly effective ligands for this reaction include l,4-bis(diphenylphosphino)butane (DPPB) 34, phosphole (o-TDPP) 35, and phosphanorbomadiene (DMTPPN) 36. 

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