Asymmetric Hydroformylation and Hydrocarboxylation of Enamides. Synthesis of Alanine and Proline

Article abstract of DOI:10.1021/jo01299a022

Carbonyltris(triphenylphosphine)hydridorhodium (1) catalyzed the hydroformylation of N-vinylimides in the presence of optically active 2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane (DIOP) or 2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(5H-dibenzophospholyl)butane (DIPHOL) to afford optically active α-amido aldehydes.Linear disubstituted N-vinylimides or -amides reacted very sluggishly, while the cyclic N-acyl-2-pyrroline (19) was very reactive.In the unsubstituted N-vinylimides moderate (20-40percent ee) asymmetric induction was observed.The optically active α-amido aldehydes were readily converted to the corresponding α-amino acids.Asymmetric hydrocarboxylation of the same substrates in the presence of bis(triphenylphosphine)palladium chloride (2) produced α-amido esters in low optical purity.