The synthesis and configurational stability of enantioenriched α-thioallyllithium compounds and the stereochemical course of their electrophilic substitution
Deprotonation of enantioenriched S-allyl N-monoalkylmonothiocarbamates furnished the corresponding chiral lithium compounds. The α-thioallyllithium compounds 9 and 25 were found to be configurationally stable in THF solutions at -78 °C. These represent the first configurationally stable α-thio-substituted allyllithium compounds, and they can be utilized in asymmetric synthesis. Alkylations proceeded with stereo-inversion or in an anti-SE′ process, while addition to carbonyl compounds took place in a syn-SE′ process. Hydroxyalkylation products were employed as starting material for Ni0-catalyzed cross-coupling reactions.
A highly enantioenriched, configurationally stable α-thioallyllithium compound and the stereochemical course of its electrophilic alkylation
matrix presented The first highly enantioenriched, configurationally stable a-thioallyllithium compound (9) was generated by deprotonation of the S-cyclohex-2-enyl thiocarbamate 8. The methylation of 9 in both the α- and γ-positions proceeds antarafacially with a high degree of chirality transmission, as was elucidated by X-ray analysis of thiocarbamates 10 and 11. The optically active S-allyl thiocarbamate 8 was prepared by enantiospecific [3,3]sigmatropic rearrangement of the corresponding Oallyl thiocarbamate 7.
Marr, Felix,Froehlich, Roland,Hoppe, Dieter
p. 2081 - 2083
(2008/02/09)
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