Bidentate gallium Lewis acids were prepared by the reaction of diethynyldiphenylsilane with neat trimethyl- or triethylgallium. Bis[(dimethylgallyl)ethynyl]diphenylsilane (1) and diethylgallyl derivative 2 were characterized as Et O or pyridine adducts by NMR spectroscopy; 2⋅2Py was isolated. Lewis acids 1 and 2 form host-guest adducts with bidentate nitrogen bases, but defined cyclic 1:1 adducts are only formed between 1 and bases with matching N⋅⋅⋅N distances: 4,4'-dimethyl-3,3'-bipyridinylacetylene (3), bis[(pyridin-3-yl)ethynyl]diphenylsilane (4), and bis[(2-methylpyridin-5-yl)ethynyl]diphenylsilane (5). The structures of adducts 1⋅3, 1⋅4, and 1⋅5 were established by X-ray diffraction experiments. 2⋅2Py reacts with DABCO to afford polymeric (DABCO-2-) .

Zweizähnige Gallium Lewis‐Säuren wurden ausgehend von Diethinyldiphenylsilan in reinem Trimethyl‐ oder Triethylgallium dargestellt. Bis[(dimethylgallanyl)ethinyl]diphenylsilan (1) und dessen Diethylgallanyl‐Derivat 2 wurden als Et2O‐ oder Pyridin‐Addukte NMR‐spektroskopisch charakterisiert; 2⋅2 Py wurde isoliert. Die Lewis‐Säuren 1 und 2 bilden Wirt‐Gast‐Addukte mit zweizähnigen Stickstoffbasen; dabei bilden sich nur bei passendem N⋅⋅⋅N‐Abstand cyclische 1:1‐Addukte aus 1 und 4,4′‐Dimethyl‐3,3′‐bipyridylacetylen (3), Bis[(pyrid‐3‐yl)ethinyl]diphenylsilan (4) oder Bis[(2‐methylpyrid‐5‐yl)ethyinyl]diphenylsilan (5). Die cyclischen Addukte 1⋅3, 1⋅4 und 1⋅5 wurde mittels Röntgenbeugungsexperimenten identifiziert. 2⋅2 Py reagiert mit DABCO zur polymeren Spezies (DABCO‐2‐)n.

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A proof of concept for a novel approach towards enantiomerically highly enriched acyclic secondary amines and β-aminothiols as non-cyclic target molecules when starting from 3-thiazolines as heterocycles is presented. Starting from 2,2,4,5,5-pentamethyl-3-thiazoline, we demonstrated this chemoenzymatic pathway to both of these types of amine molecules, which were isolated as urea derivatives with a non-optimized yield of up to 20%. As a substrate, 2,2,4,5,5-pentamethyl-3-thiazolidine, which was obtained with an enantiomeric excess (ee) of 99% in a biotransformation from the corresponding 3-thiazoline according to a recently developed protocol, was used. For the reductive desulfurization of this substrate leading to a sulfur-free secondary amine, in situ formed Ni2B turned out to be a suitable reducing reagent. However, when using lithium aluminum hydride as a reducing agent, β-aminothiol was obtained.

Matching the Ga⋅⋅⋅Ga distance of a bidentate gallium Lewis acid to the N⋅⋅⋅N distance of a bidentate nitrogen base allows the formation of a cyclic 1:1 adduct. The design of suitable bidentate Lewis acids is described in the Communication by N. W. Mitzel et al. on page 6107 ff. In the picture, the element gallium is symbolized by gallus (the cock, a symbol of France) and nitrogen by air in the sky above the mountains (view over Fimba Valley, Tyrol).