Kadri Kriis

A Novel Diastereoselective Multicomponent Cascade Reaction

A novel multicomponent cascade reaction led to the formation of a strained 3-azabicyclo[3.2.0]heptane derivative 4. The unstable ester 4 was reduced in a one-pot procedure to a stable alcohol 6. The formation of the bicyclic product is highly diastereoselective, predominantly affording one diastereoisomer. The obtained azabicycloheptanes are important pharmacophores.

Asymmetric oxidation of cyclobutanones: modification of the Sharpless catalyst

Abstract Oxidation of prochiral and racemic cyclobutanones with t-BuOOH and Ti–TADDOL-based complexes afforded lactones in up to 44% ee. The enantioselectivity of the reaction clearly depends on the amount of the reagent and the highest enantioselectivities were obtained with stoichiometric amounts of the complex. Modification of the TADDOL structure and use of the mixed complex derived from TADDOL and a tartaric ester led to more reactive but less selective oxidation systems.

Chemoenzymatic synthesis and evaluation of 3-azabicyclo[3.2.0]heptane derivatives as dopaminergic ligands.

New 3-azabicyclo[3.2.0]heptane derivatives were synthesized using a multicomponent reaction. Racemic compounds were efficiently resolved by kinetic resolution with immobilized lipase B of Candida antarctica (Novozym 435). The obtained compounds demonstrated greater binding affinity at D(2L) and D(3) dopamine receptors compared to D(1) binding sites, and individual enantiomers of the same compound possessed distinct affinities.

Asymmetric synthesis of novel C2-symmetric bimorpholines

Abstract Novel heterocycles—(2S,2′S)-bimorpholine 1 and (3S,3′S)-bimorpholine 2—were synthesised in >98% e.e. starting from tartaric acid ester.

Synthesis and Characterisation of Chiral Triazole‐Based Halogen‐Bond Donors: Halogen Bonds in the Solid State and in Solution

A general platform for the synthesis of various chiral halogen-bond (XB) donors based on the triazole core and the characterisation of factors that influence the strength of the halogen bond in the solid state and in solution are reported. The characterisation of XB donors in the solid state by X-ray crystallography and in solution by 1 H NMR titration can be used to aid the design of new XB donors. We describe the first example of a XB between iodotriazoles and thioureas in solution. In addition, the enantiodiscrimination of acceptors in solution through halogen-bond participation is described.

Diastereoselective Multicomponent Cascade Reaction Leading to [3.2.0]-Heterobicyclic Compounds

A general three-component triple cascade reaction through an iminium-enamine-iminium sequential activation initiated by a hetero-Michael addition to α,β-unsaturated aldehydes affords [3.2.0]heterobicycles in high diastereoselectivity. The rate and diastereoselectivity of the reaction depended on the (E)-4-heterocrotonate and size of the secondary amine. The enantiomers of the major diastereoisomer of oxa- and azabicyclo[3.2.0]heptane derivatives were separated by enzymatic kinetic resolution with immobilized Candida antarctica Lipase B (CALB), with E values up to 153. The absolute configuration of the nonacylated enantiomer of oxabicyclo[3.2.0]heptane was determined by single crystal X-ray analysis.

C2-Symmetric bimorpholines as chiral ligands in the asymmetric hydrogenation of ketones

Abstract 2,2′-Bimorpholine and 3,3′-bimorpholine were used as chiral ligands in Rh-mediated asymmetric hydride transfer reduction of prochiral aromatic ketones affording corresponding alcohols with good ee (up to 75%).