Catalytic Asymmetric Michael Reaction of -Catalytic Asymmetric Michael Reaction of -KetoKeto Esters: Esters:Effects of the LinkerEffects of the Linker Heteroatom Heteroatom in Linked-BINOL in Linked-BINOLKeisuke Majima, Ryo Takita, Akihiro Okada, Takashi Ohshima,and Masakatsu Shibasaki*Contribution from the Graduate School of Pharmaceutical Sciences, TheUniversity of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, JapanJ. Am. Chem. Soc. 2003, 125, 15837-15845Professor Masakatsu Shibasakihttp://www.sigmaaldrich.com/suite7/Brands/Fluka___Riedel_Home/Miscellaneous/Reagent_of_the_Year/1996.htmlReagent of the year 1996Review: Matsunaga, S.; Ohshima, T.; Shibasaki, M. Adv. Synth. Catal. 2002, 1, 344Catalytic asymmetric Michael reactionPreparation:La(OiPr)3 + NR-Linked-BINOLRemove solventLa-NR-Linked-BINOLPale-yellow powderLSB: Lanthanide-containing chiralheterometallic complexALB: Aluminum-containing chiralheterobimetalliccomplexConclusion1. Asymmetric induction occurs at the beta-position of Michael acceptor was achieved by usingLa-NR-linked-BINOL (R=H or Me) complex2. A linker heteroatom in linked-BINOL can tune the catalyst profile electronically andsterically. In general, NMe ligand 2 was suitable for the combination of both small enonesand beta-keto esters, and the NH ligand 1 was suitable for bulkier substrate.3. To generate the desired active species effectively, maintaining the ration of the La-NMe-linked-BINOL complex and beta-keto ester at 1:2 to 1:10 was very
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