Bidentate Boron‐Lewis Acids – Selectivity in Host‐Guest Complex Formation

Bidentate boron‐Lewis acids based on 1,8‐diethynylanthracene were synthesised in two steps by initial stannylation of the terminal alkynes and subsequent tin‐boron exchange with different chloroboranes. The reactions are very selective and the target com¬pounds were obtained in high purity and good to excellent yields. Complexation experiments of 1,8‐bis[(diphenylboraneyl)ethynyl]anthracene with nitrogen bases (pyridine, pyrimidine, TMEDA) afforded stable adducts. Three adducts were structurally characterised by X‐ray diffraction. Competition experiments demonstrated the exchange of guests and quantum‐chemical calculations provided infor‐mation on their energetics. NMR experiments at low temperatures gave insight into the dynamic behaviour of the TMEDA adduct.

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