219701-11-8Relevant academic research and scientific papers
Diastereoselectivity in the boron aldol reaction of α-alkoxy and α,β-bis-alkoxy methyl ketones
Fernandes, Alessandra A. G.,Leonarczyk, Ives A.,Ferreira, Marco A. B.,Dias, Luiz Carlos
, p. 3167 - 3180 (2019/03/26)
In this work, using DFT calculations, we investigated the 1,4 and 1,5 asymmetric induction in boron enolate aldol reactions of α-alkoxy and α,β-bisalkoxy methyl ketones. We evaluated the steric influence of alkyl substituents at the α position and the stereoelectronic influence of the oxygen protecting groups at the α and β positions. Theoretical calculations revealed the origins of the 1,4 asymmetric induction in terms of the nature of the β-substituent. The synergistic effect between the α,β-syn and α,β-anti-bisalkoxy stereocenters was elucidated. In the presence of the β-alkoxy center, the reaction proceeds through the Goodman-Paton 1,5-stereoinduction model, experiencing a minor influence of the α-alkoxy center.
Stereoselective acetate aldol reactions of α-silyloxy ketones
Lorente, Adriana,Pellicena, Miquel,Romea, Pedro,Urpí, Fèlix
, p. 1023 - 1035 (2015/01/30)
TiCl4-mediated aldol reactions of chiral methyl α-silyloxy ketones with a variety of aldehydes provide the corresponding 1,4-syn aldol adducts with moderate to high stereocontrol. This transformation represents a new approach to substrate-controlled acetate aldol reactions and complements the 1,4-anti asymmetric induction produced by the related α-benzyloxy ketones. This new approach could be useful in the design of more efficient syntheses of natural products.
1,4-syn-Asymmetric induction in the titanium-mediated aldol reactions of chiral methyl α-silyloxy ketones
Lorente, Adriana,Pellicena, Miquel,Romea, Pedro,Urpí, Fèlix
experimental part, p. 942 - 945 (2010/04/29)
Good levels of 1,4-syn asymmetric induction are obtained in the TiCl4-mediated aldol reaction of methyl α-silyloxy ketones with achiral aldehydes. Such methodology represents a new approach to the substrate-controlled acetate aldol reaction, which can be useful to design more efficient syntheses of natural products.
The chemistry of trichlorosilyl enolates. Aldol addition reactions of methyl ketones
Denmark,Stavenger
, p. 8837 - 8847 (2007/10/03)
Investigations on the aldol addition chemistry of trichlorosilyl enolates derived from methyl ketones are presented in full. These trichlorosilyl enolates are competent aldol reagents in the absence of additives, reacting with aldehydes at ambient temperature to provide high yields of aldol adducts. When either enol or aldehyde partner bears a stereogenic center, low diastereoselectivity is observed in this uncatalyzed aldol process. The aldol additions are dramatically accelerated by the addition of catalytic quantities of chiral phosphoramides, particularly one derived from N,N'-dimethylstilbene-1,2-diamine. In this catalyzed mode, good to high enantioselectivities are obtained with a variety of achiral trichlorosilyl enolates and aldehydes. When either partner bears a stereogenic center, high diastereoselectivities are obtained with one enantiomer of the catalyst (matched case), while the other enantiomer provides low diastereoselectivity (mismatched case). The reaction scope, optimization of conditions, and stereoselection events are also discussed.
