188400-02-4Relevant articles and documents
Palladium(0)-catalyzed enantioselective O,S-rearrangement of racemic O-allylic thiocarbamates: A new entry to enantioenriched allylic sulfur compounds
Gais, Hans-Joachim,Boehme, Achim
, p. 1153 - 1161 (2002)
Reaction of (±)-(E)-pent-3-en-2-ol, (±)-(E)-hept-4-en-3-ol, (±)-(E)-2,6-dimethylhept-4-en-3-ol, (±)-cyclohex-2-en-1-ol, and (±)-cyclohept-2-en-1-ol with methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, and benzyl isothiocyanate gave the corresponding racemic O-allylic thiocarbamates of medium to good thermal stability in good yields. The palladium(0)-catalyzed rearrangement of the (±)-(E)-pent-3-en-2-ol-, (±)-(E)-hept-4-en-3-ol-, (±)-cyclohex-2-en-1-ol-, and (±)-cyclohept-2-en-1-ol-derived O-allylic thiocarbamates at room temperature in methylene chloride by using Pd2(dba)3·CHCl3 (dba = dibenzylideneacetone) as precatalyst and (+)-(1R,2R)-1,2-bis-N-((2-(diphenylphosphino)benzoyl)-1,2-diaminocyclohexane as ligand for the palladium atom proceeded quantitatively and gave the corresponding acyclic (R)-configured S-allylic thiocarbamates and the cyclic (S)-configured S-allylic thiocarbamates with ee values ranging from 85% to ≥99% in yields of 76-94%. Rearrangement of the O-allylic thiocarbamates carrying a methyl group at the N atom not only was the fastest but also proceeded with the highest enantioselectivity. No rearrangement was observed under these conditions in the case of the racemic N-methyl O-allylic thiocarbamate derived from (±)-2,6-dimethylhept-4-en-3-ol, which has a branched carbon skeleton. (S)-Cyclohex-2-enethiol of 97% ee was obtained through hydrolysis of the corresponding N-methyl S-allylic thiocarbamate. 2-((R)-(E)-1-Methylbut-2-enylsulfanyl)pyrimidine of 91% ee and 2-((S)-cyclohex-2-enylsulfanyl)pyrimidine of 97% ee were synthesized in one synthetic operation from the corresponding N-methyl S-allylic thiocarbamates and 2-chloropyrimidine. Similarly, (S)-cyclohex-2-enylsulfanyl)benzene of 97% ee was obtained in one synthetic operation from the corresponding N-methyl S-allylic thiocarbamate through a palladium(0)-catalyzed substitution of iodobenzene in the presence of a base. The palladium(0)-catalyzed enantioselective rearrangement of O-allylic carbamates to S-allylic carbamates has been extended from the solution phase to the solid phase by using a methyl thioisocyanate polystyrene resin. In the case investigated the enantioselectivity of the rearrangement on the solid phase was considerably lower than that in solution.
The synthesis and configurational stability of enantioenriched α-thioallyllithium compounds and the stereochemical course of their electrophilic substitution
Marr, Felix,Froehlich, Roland,Wibbeling, Birgit,Diedrich, Christian,Hoppe, Dieter
, p. 2970 - 2988 (2007/10/03)
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.
