The synthesis of bench-stable α,α-bis(trimethylsilyl)toluenes and tris(trimethylsilyl)methane is described and their use in stereoselective Peterson olefinations has been achieved with a wide substrate scope. Product stereoselectivity was poor with carbonyl electrophiles (E/Z ∼1:1 to 4:1) though this was significantly improved by employing the corresponding substituted N-benzylideneaniline (up to 99:1) as an alternative electrophile. The olefination byproduct was identified as N,N-bis(trimethylsilyl)aniline and could be easily separated from product by aqueous acid extraction. Evidence for an autocatalytic cycle has been obtained.
We disclose the first total synthesis of stachybotrin C, a potent neuroprotective natural compound. All of the four stereoisomers have been prepared and fully characterized with the aim to attribute the absolute configuration of the two adjacent stereocenters of the stachybotrin C.
A novel
direct and diastereoselective amination of biosourced monobenzylated
isohexides has been developed through borrowing hydrogen methodology
using a cooperative catalysis between an iridium complex and a phosphoric
acid. We also report herein the first regio- and diastereoselective
direct amination of isosorbide.
We report a TMSI-promoted Prins cyclization reaction with ketones as carbonyl partners to prepare polysubstituted chiral spirotetrahydropyrans. In the presence of racemic 2-methylcyclohexanone a dynamic kinetic resolution occurred affording one stereoisomer. The observed enantiospecificity has been rationalized by DFT calculation.
The regio and diastereoselective direct mono or diamination of bio-based isohexides (isosorbide and isomannide) has been developed through borrowing hydrogen (BH) methodology using a cooperative catalysis between an iridium com-[a] Univ Lyon,
The preparation of racemic des-hydroxy stachybotrin C is described. Different approaches have been studied. Observations made in the course of the synthesis show the efficiency of the intermolecular cyclization between the diethyl acetal 19 and phenol 12 leading to the benzopyran moiety 17.
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