Trans-cycloalkenes with the X–C=C–SeR*-unit and ring sizes from 9 to 20 have been synthesized. Bond the selenium atom is the chiral (S)-o-(1-Methoxypropyl)phenyl-residue R*, and X = H, F, Cl, Br, I, Me, Et and CF3. The planar-chiral trans-cycloalkenes in combination with the chiral residue R* exist as two diastereomers. These can be distinguished in principle by NMR spectroscopy. We have studied the epimerization of the trans-cycloalkenes, i.e., the 180° rotation of the X–C=C-unit through the cavity of the ring. The measurements were done with variable temperature 13C NMR spectroscopy in the range from –110 to 140°C. The obtained values of the Gibbs energy of activation ΔG‡C depend strongly on the ring size. Furthermore, the ΔG‡C values show dramatic steric effects due to the groups X. The steric requirement of X increases in the series H << F << Cl < Me < Br < I < Et < CF3. Here, F is significantly larger than H, and CF3 is larger than Et. The corresponding iPr-compounds could not be synthesized. The transition state structures of the ring inversion for ring sizes 8–20 were calculated at the DFT level of theory.

In the presence of cesium carbonate, ynones bearing an ortho-amino group reacted with cyclic β-ketoesters through conjugated addition/carbon-carbon σ-bond cleavage/nucleophilic aromatic substitution tandem reaction to obtain 4-quinolones fused with medium-sized rings in good yields. This is the first example of synthesis of 4-quinolones through base-promoted insertion reactions of carbon-carbon triple bonds into carbon-carbon σ-bonds. Notable features of this program are mild and transition-metal-free reaction conditions.

An efficient catalyst-free C-O bond formation reaction for the synthesis of 1H-indol-3-yl benzoates was developed through C(sp2)-H functionalization of 1H indoles with benzoyl peroxide (BPO) in acetonitrile at room temperature under open flask conditions. The reaction proceeds without exclusion of air or moisture and is applied to a wide array of electronically differentiated indoles as well as BPOs. C-3 benzoxylation of indoles was achieved with excellent regioselectivity under mild and easy to operate conditions. The reaction is scalable to one gram level.

Herein, we have disclosed a feasible approach to access oxygen bridged tricyclo fused cyclopropane derivatives via visible light mediated photoredox catalyzed energy transfer process. This protocol describes one step multi-fused ring formation under mild reaction conditions to furnish a wide range of the fused cyclopropane derivatives in moderate to high yields with excellent diastereoselectivities.

A process concept for the asymmetric biocatalytic reduction of heterocyclic imines addressing the efficiency of the reaction as well as downstream-processing steps was studied by utilizing a “heterogenized aqueous phase”, which contains the needed enzymes and cofactor within a superabsorber (polyacrylate) network, for the biotransformation. The immobilized biocatalytic system, which comprises an imine reductase IRED, NADPH and an alcohol dehydrogenase for cofactor-recycling, enables to run the reaction in pure organic medium. Thus, instead of an extractive work-up as typical solution for biotransformations in aqueous medium, which, however, can be tedious due formation of emulsions, this type of IRED-catalyzed process leads to a simplified work-up consisting only of a decantation of the liquid organic reaction medium with the product from the heterogenized aqueous biocatalyst system. Exemplified for the (R)-enantioselective reduction of 1-methyl-3,4-dihydroisoquinoline by the IRED of Streptomyces viridochromogenes as a model reaction, a process was developed leading to 98% conversion, 88% yield and >99% ee at a substrate concentration of 40 mM.