The amide moiety of peptides can be replaced for example by a triazole moiety, which is considered to be bioisosteric. Therefore, the carbonyl moiety of an amino acid has to be replaced by an alkyne in order to provide a precursor of such peptidomimetics. As most amino acids have a chiral center at Cα, such amide bond surrogates need a chiral moiety. Here the asymmetric synthesis of a set of 24 N-sulfinyl propargylamines is presented. The condensation of various aldehydes with Ellman’s chiral sulfinamide provides chiral N-sulfinylimines, which were reacted with (trimethylsilyl)ethynyllithium to afford diastereomerically pure N-sulfinyl propargylamines. Diverse functional groups present in the propargylic position resemble the side chain present at the Cα of amino acids. Whereas propargylamines with (cyclo)alkyl substituents can be prepared in a direct manner, residues with polar functional groups require suitable protective groups. The presence of particular functional groups in the side chain in some cases leads to remarkable side reactions of the alkyne moiety. Thus, electron-withdrawing substituents in the Cα-position facilitate a base induced rearrangement to α,β-unsaturated imines, while azide-substituted propargylamines form triazoles under surprisingly mild conditions. A panel of propargylamines bearing fluoro or chloro substituents, polar functional groups, or basic and acidic functional groups is accessible for the use as precursors of peptidomimetics.

Starting from 1,2‐diethynylbenzene, a series of bidentate Lewis acids was prepared by means of hydrometalations, in particular hydrosilylation, hydroboration, hydroalumination and terminal metalation based on group 13 and 14 elements. In the case of terminal alkyne metalation, the Lewis‐acidic gallium function was introduced using triethylgallium under alkane elimination. A total of six different Lewis acids based on a semiflexible organic scaffold were prepared, bearing −SiClMe 2 , −SiCl 2 Me, −SiCl 3 , −B(C 6 F 5 ) 2 , −AlBis 2 (Bis=bis(trimethylsilyl)methyl) and −GaEt 2 as the corresponding functional units. In all cases, the Lewis acid functionalisation was carried out twice and the products were obtained in good to excellent yields. In the case of the twofold gallium Lewis acid, a different structural motif in the form of a polymer‐like chain was observed in the solid state. All new bidentate Lewis acids were characterised by multinuclear NMR spectroscopy, CHN analysis and X‐ray diffraction experiments.

Three bifunctional boron‐Lewis acids based on a 1,2‐diethynylbenzene backbone were synthesized using a tin‐boron exchange protocol in good to very good yields. Complexation experiments with pyrimidine were thoroughly investigated using the example of 1,2‐bis(benzo[d][1,3,2]dioxaborol‐2‐ylethynyl)benzene (3) in solution, in the solid phase and by quantum‐chemical calculations. Two adducts were structurally investigated by X‐ray diffraction experiments. DOSY‐/VT‐NMR experiments gave insight into the dynamic behaviour of the synthesized poly‐Lewis acids with pyrimidine.

Based on a semiflexible trisilacyclohexane framework a series of directed, tridentate Lewis acids were synthesized by hydrosilylation using various (chloro)methylsilanes. The axial alignment of the three electron deficient functions in one spatial direction allows creating poly-Lewis acids with chalice-like cavities. The directed, tridentate poly-Lewis acids were obtained in quantitative yields and characterized by multinuclear NMR spectroscopy, CHN analysis and X-ray diffraction experiments. The Lewis acidity of the introduced silicon functions was quantified and classified using the Gutmann-Beckett method.

Based on the previously described bifunctional Lewis acid with a functional distance of the boron functions of 4.918(2) Å, the development of a further bifunctional, boron-containing Lewis acid with a wider functional distance is demonstrated. Again, a stannylated precursor was used and the Lewis-acidic boron functions were introduced by means of tin-boron exchange. The general suitability of this class of compounds for the formation of host-guest-complexes is demonstrated by NMR experiments and by solid-state structures using pyridine and TMPD (N 1,N 1,N 4,N 4-tetramethylbenzene-1,4-diamine) as Lewis basic guests. The influence of traces of moisture on the boron-containing, bifunctional Lewis acids was investigated by the structure elucidation of a decomposition product.