Herein, we report a double deprotonation method used for the preparation of ynolates starting from nonbrominated 2,6-di-tert-butylphenyl esters. The current method is superior to the previously described double lithium/halogen exchange approach because easily accessible starting materials are used. This method will be especially useful for preparation of ynolates bearing functional groups in organic
and trialkyl-substituted alkenes undergo carboxylation with CO2 in the presence of EtAlCl2 and 2,6-dibromopyridine to afford the corresponding α,β- and/or β,γ-unsaturated carboxylic acids. This reaction is suggested to proceed via the electrophilicsubstitution of EtAlCl2 with the aid of the base, followed by the carbonation of the resulting ate complex. This reaction can be applied to terminal dialkylalkenes
Ynolates react with ketones at room temperature to afford α,β,β-trisubstituted acrylates (tetrasubstituted olefins) with 2:1−8:1 geometrical selectivities. This can be regarded as a new olefination reaction of ketones giving tetrasubstituted olefins in good yield, even in the case of sterically hindered substrates. The reaction mechanism involves cycloaddition of ynolates with a carbonyl group and
Palladium-Catalyzed Fluoride-Free Cross-Coupling of Intramolecularly Activated Alkenylsilanes and Alkenylgermanes: Synthesis of Tamoxifen as a Synthetic Application
作者:Kenji Matsumoto、Mitsuru Shindo
DOI:10.1002/adsc.201100627
日期:2012.3
intramolecular hypercoordination of a carboxylic acid is a powerful activation strategy for the palladium‐catalyzed cross‐coupling reaction of trialkyl(vinyl)silanes and trialkyl(vinyl)germanes under fluoride‐free conditions. Z‐β‐Trialkylsilyl‐ and Z‐β‐trialkylgermylacrylic acids, synthesized stereoselectively by olefination with ynolates, are highly stable and useful reagents for cross‐coupling with a variety
Reductive lithiation of α,α-dibromo esters using lithium naphthalenide afforded ester dianions leading to ynolateanions in good yields. Naphthalene-catalyzed reductive lithiation was also accomplished. This is a convenient, economical and practical method for the preparation of ynolateanions.