212050-32-3Relevant academic research and scientific papers
Direct catalytic asymmetric aldol reactions promoted by a novel barium complex
Yamada, Yoichi M. A.,Shibasaki, Masakatsu
, p. 5561 - 5564 (1998)
A direct catalytic asymmetric aldol reaction of an aldehyde and an unmodified ketone promoted by an asymmetric barium complex has been achieved. The possible structure of the barium catalyst, BaB-M, which possesses the function of a Lewis acid and a Brons
Catalytic asymmetric aldol reaction of ketones and aldehydes using chiral calcium alkoxides
Suzuki, Takeyuki,Yamagiwa, Noriyuki,Matsuo, Yoshimi,Sakamoto, Shigeru,Yamaguchi, Kentaro,Shibasaki, Masakatsu,Noyori, Ryoji
, p. 4669 - 4671 (2007/10/03)
A chiral hydrobenzoin/Ca complex catalyzes the reaction of acetophenone and aliphatic aldehydes to give the corresponding aldol products in up to 91% ee.
Direct catalytic asymmetric aldol reaction
Yoshikawa, Naoki,Yamada, Yoichi M. A.,Das, Jagattaran,Sasai, Hiroaki,Shibasaki, Masakatsu
, p. 4168 - 4178 (2007/10/03)
The direct catalytic asymmetric aldol reaction using aldehydes and unmodified ketones is described for the first time herein. This reaction was first found to be promoted by 20 mol % of anhydrous (R)-LLB (L = lanthanum, L = lithium, B = (R)-binaphthol moiety) at -20 °C, giving a variety of aldol products in ee's ranging from 44 to 94%. This asymmetric reaction has been greatly improved by developing a new heteropolymetallic asymmetric catalyst [(R)-LLB, KOH, and H2O]. Using 3-8 mol % of this catalyst, a variety of direct catalytic asymmetric aldol reactions were again found to proceed smoothly, affording aldol products in ee's ranging from 30 to 93% and in good to excellent yields. Interestingly, the use of this new heteropolymetallic asymmetric catalyst has realized a diastereoselective and enantioselective aldol reaction using cyclopentanone for the first time. It is also noteworthy that a variety of aldehydes, including hexanal, can be utilized for the current direct catalytic asymmetric aldol reaction. Chiral aldehydes containing α-hydrogen including (S)-hydrocinnamaldehyde-α-d have been found to produce the corresponding aldol products with negligible racemization (0-4%) at the α-position. One of the aldol products has been successfully converted to the key synthetic intermediates of epothilone A and bryostatin 7. The possible structure of the heteropolymetallic catalyst is also discussed. Finally, mechanistic studies have revealed a characteristic reaction pathway, namely that the reaction is kinetically controlled and the rate-determining step is the deprotonation of the ketone. This is consistent with the fact that the reaction rate is independent of the concentration of the aldehyde.
