Enantiomerically pure bis-1,3-dioxolanylmethyl chalcogenides and dichalcogenides (S, Se and Te) were prepared from chalcogenides and chiral solketal tosylates.
A new class of bifunctional organocatalysts containing both thiazolidine/pyrrolidine and imidazole cycles was prepared via a readily available synthetic route.
An important contribution to the field of asymmetric catalysis is described in this work, as it merges the search for new ligands that can provide high performance in asymmetric catalysis with the extremely important and increasing need for sustainability. New chiral ionic liquids have been synthesised from the amino acid l‐cysteine by straightforward routes. With these ligands, we have developed a chiral ionic system that includes chiral ionic liquids and their immobilisation in ionic solvents to provide a chiral supramolecular structure. These new catalytic systems were used in the enantioselective addition of alkylzinc to aldehydes and proved to be very efficient, capable of providing chiral secondary alcohols in excellent enantiomeric excesses and yields. This system also enabled the recycling of the ionic media and the ionic ligand, taking into account green chemistry considerations.
This work investigates the support of organocatalysts in polyesters, a class of polymers seldom used for this purpose. The proposal is to use the hydroxyl groups present in the structure of the chosen chiral compounds to promote the polymerization of ε-caprolactone, generating the support and anchoring the organocatalyst in a single step. A very simple method, with acid catalysis, was employed, that showed versatility in generating supported catalysts with different structures and functional groups and modulating the mass of the materials to generate specific solubility characteristics. In this way, the catalysts can be solubilized in some organic solvents, such as dichloromethane, but at the end of the reaction, they can be recovered in a heterogeneous way, through precipitation in more apolar solvents. The materials were applied as organocatalysts on an aldol addition test reaction and the product could be obtained in excellent yields and good stereoselectivity. The polymer did not show signs of degradation after the reaction, proving to be robust and suitable for use in catalysis; however, a recycling process appears to be necessary for its reuse.
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