Catalytic asymmetric 1,4-addition reactions using alpha,beta-unsaturated N-acylpyrroles as highly reactive monodentate alpha,beta-unsaturated ester surrogates.
Synthesis and application of alpha,beta-unsaturated N-acylpyrroles as highly reactive, monodentate ester surrogates in the catalytic asymmetric epoxidation and Michael reactions are described. alpha,beta-Unsaturated N-acylpyrroles with various functional groups were synthesized by the Wittig reaction using ylide 2. A Sm(O-i-Pr)(3)/H(8)-BINOL complex was the most effective catalyst for the epoxidation to afford pyrrolyl epoxides in up to 100% yield and >99% ee. Catalyst loading was successfully reduced to as little as 0.02 mol % (substrate/catalyst = 5000). The high turnover frequency and high volumetric productivity of the present reaction are also noteworthy. In addition, a sequential Wittig olefination-catalytic asymmetric epoxidation reaction was developed, providing efficient one-pot access to optically active epoxides from various aldehydes in high yield and ee (96-->99%). In a direct catalytic asymmetric Michael reaction of hydroxyketone promoted by the Et(2)Zn/linked-BINOL complex, Michael adducts were obtained in good yield (74-97%), dr (69/31-95/5), and ee (73-95%). This represents the first direct catalytic asymmetric Michael reaction of unmodified ketone to an alpha,beta-unsaturated carboxylic acid derivative. The properties of alpha,beta-unsaturated N-acylpyrrole are also discussed. Finally, the utility of the N-acylpyrrole unit for further transformations is demonstrated.
Matsunaga
Shigeki
S
Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Kinoshita
Tomofumi
T
Okada
Shigemitsu
S
Harada
Shinji
S
Shibasaki
Masakatsu
M
D002384:Catalysis; D004852:Epoxy Compounds / Q000138:chemical synthesis / Q000737:chemistry; D004952:Esters / Q000138:chemical synthesis / Q000737:chemistry*; D015394:Molecular Structure; D011758:Pyrroles / Q000138:chemical synthesis* / Q000737:chemistry
D004852:Epoxy Compounds; D004952:Esters; D011758:Pyrroles