Tandem Conjugate Addition−Elimination for the Diastereoselective Synthesis of 4E-Alkenyl syn-1,3-Diols
摘要:
We have developed a tandem conjugate addition-elimination sequence for the diastereoselective synthesis of protected allylic syri-1,3-diols, starting from vinyl sulfones. The sulfonyl group was then reduced with sodium amalgam to furnish the E-olefin as the major isomer. This method was applied to the synthesis of a trisubstituted alkene modeling the C21-C25 fragment of Dolabelide C.
A short route to sulfones 9a–c is described. These synthons encompassing a syn 1,3-diol motif are model compounds for the C16–C24 fragment of Dolabelides. The benzylidene protecting group can be reduced regioselectively to furnish β-hydroxysulfones 10a–b. First attempts of Julia coupling of the dianions derived from these substrates with aldehydes and ketones are also reported.
It was found that the desulfonylation reaction of α,α-dialkylated (E)-allylic sulfones with a base preferentially affords the sterically unfavorable (Z)-alkadienes. The relative degree of the “syn-effect”, which is herein defined as an effect which stabilizes the syn-conformation, leading to (Z)-products, in the transition state against the steric hindrance, was revealed for various substituents at the δ-position of the (E)-allylic sulfones to be as follows: RO– >> CH3– > RS– > –CH2– > (CH3)2CH– >> (CH3)3C– > C6H5–. This finding is in accord with a previously found tendency in the conversion of (E)-vinylic sulfones to the corresponding allylic sulfones under basic conditions.
Diastereoselective synthesis of trifluoromethylated 1,3-dioxanes by intramolecular oxa-Michael reaction
作者:Liliana Becerra-Figueroa、Elodie Brun、Michael Mathieson、Louis J. Farrugia、Claire Wilson、Joëlle Prunet、Diego Gamba-Sánchez
DOI:10.1039/c6ob02333a
日期:——
A highly diastereoselectivesynthesis of trifluoromethylated 1,3-dioxanes is described. The reaction proceeds by an addition/oxa-Michael sequence and works efficiently under mild reaction conditions, with a good substrate scope and acceptable to good yields.
Water-Compatible Synthesis of 2-Trifluoromethyl-1,3-Dioxanes
作者:Liliana Becerra-Figueroa、Alexander F. Tiniakos、Joëlle Prunet、Diego Gamba-Sánchez
DOI:10.1002/ejoc.201801367
日期:2018.12.31
A water-compatible method for the diastereoselective synthesis of 2-trifluormethyl-1,3-dioxanes is described. The reaction proceeds under mild reaction conditions using simple inorganic bases; it has a very good substrate scope and can be performed with different Michael acceptors. Additionally, the reaction products can be further functionalized, showing an excellent perspective for future applications
Tandem Conjugate Addition−Elimination for the Diastereoselective Synthesis of 4<i>E</i>-Alkenyl <i>syn</i>-1,3-Diols
作者:Delphine Rotulo-Sims、Joëlle Prunet
DOI:10.1021/ol701624y
日期:2007.10.1
We have developed a tandem conjugate addition-elimination sequence for the diastereoselective synthesis of protected allylic syri-1,3-diols, starting from vinyl sulfones. The sulfonyl group was then reduced with sodium amalgam to furnish the E-olefin as the major isomer. This method was applied to the synthesis of a trisubstituted alkene modeling the C21-C25 fragment of Dolabelide C.