A New Synthesis of Triphenylphosphorane Ylide Precursors to α-Keto Amide/Ester and Tricarbonyl Units via Horner-Wadsworth-Emmons Reaction

Newly developed Horner-Wadsworth-Emmons (HWE) reagents 5 having triphenylphosphorane ylide subunits readily condensed with various carbonyl compounds under mild reaction conditions to afford β,γ-unsaturated α-keto triphenylphorane ylides in good to excellent yields, which were hydrogenated over Pd-C (10%)/H2 (1 atm) to give the corresponding α-keto triphenylphorane ylides in quasi-quantitative yields. These triphenyphosphorane ylides have been utilized as the precursors to α-keto amide/ester and vicinal tricarbonyl units in Wasserman's synthetic protocols, and have previously been prepared only from carboxylic acids/acid chlorides. Our new approaches provide excellent alternatives for the synthesis of triphenylphosphorane ylide precursors to α-keto amide/ester and vicinal tricarbonyl units directly from carbonyl compounds in good to excellent yields