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.
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
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.