87696-52-4Relevant academic research and scientific papers
Stereoselective halo-succinimide mediated γ-halogenations of substituted α-trialkylsilyl-β,γ-unsaturated esters
Fealy, Lisa M.,Jennings, Michael P.
, (2019/11/28)
The halogenation of various α-ester allylsilanes with halo-succinimides (NXS, X = Cl, Br, and I) has been investigated. It has been shown that these reactions readily allow for good yields and excellent diastereoselectivities (up to >20:1) for a series of α-ester allylsilanes and halo-succinimide reagents, thereby providing a straightforward approach of preparing γ-halo-(E)-α,β-unsaturated esters.
Diastereoselective Syntheses of (E)-α-Trialkylsilyl α,β-Unsaturated Esters, α-Silane-Substituted Conjugated Silyl Ketene Acetals, and α,γ-Substituted Allylsilanes
Johnson, David A.,Mueller Hendrix, Amanda J.,Jennings, Michael P.
, p. 9914 - 9928 (2018/08/03)
The vicinal functionalization of propiolate esters via a catalytic carbocupration/silicon group migration sequence has been further investigated to include the syntheses of a wide variety of β-alkyl- and β-aryl-substituted (E)-α-silyl α,β-unsaturated esters. The ester substrates were transformed into their β, γ-unsaturated isomers by means of an LDA-mediated γ-deprotonation, extended silyl ketene acetal formation, and final α-protonation sequence. The silyl ketene acetal intermediates were also isolated, and their stereochemistries were established by NOE. The isolation of the intermediate extended silyl ketene acetals afforded further understanding of the lithium-extended dienolate structure and furnished additional support for Snieckus's proposed cyclic eight-membered transition state in the deprotonation of (Z)-α,β-unsaturated carbonyls with metallodialkylamides.
Selective γ-Substitution of α,β-Unsaturated Esters via α-Trimethylsilyl β,γ-Unsaturated Esters
Albaugh-Robertson, Pamela,Katzenellenbogen, John A.
, p. 5288 - 5302 (2007/10/02)
In order to achieve selective γ-substitution of α,β-unsaturated esters, we investigated the directive effect of silicon in the reaction of various electrophiles with α-trimethylsilyl β,γ-unsaturated esters.These esters were prepared by nickel-catalyzed vinylation reactions of the lithium enolate of ethyl α-(trimethylsilyl)acetate.The α-silyl β,γ-unsaturated esters reacted with a variety of electrophiles (aldehydes, ketones, acetals, ketals, acid chlorides, and chloro thioethers) in the presence of Lewis acids (titanium tetrachloride and trimethylsilyl trifluoromethanesulfonate) to give exclusively the γ-substituted product in moderate to good yields.In some cases, the primary substitution products underwent additional conversions under the reaction conditions, such as the cyclization of the δ-hydroxyl or δ-keto enoates to dihydropyrones or pyrones, respectively.These α-silyl β,γ-unsaturated esters are effective reagents for achieving complete γ-selective substitution of α,β-unsaturated ester systems.
