From Azole—Borane Adducts to Azaboles — Molecular Structure of an Imidazabole

Elimination of H 2 from the imidazole—borane adduct 1 leads to a mixture of the imidazaboles 2 and 2 ′. The symmetrical isomer 2 (two H 2 BNC fragments) is isolated in pure state and characterized by an X‐ray structure analysis (monoclinic, space group P 2 1 ). 2‐(Trimethylstannyl)thiazole ( 3a ) and 1‐methyl‐5‐(trimethylstannyl)‐1,2,4‐triazole ( 3b ) react with triethylborane to form adducts 4 from which, in the presence of an excess of Et 3 B, tetraalkyltin is elimated to give the thiazabole 5a and the triazabole 5b , respectively. Multinuclear 1 H‐, 11 B‐, 13 C‐, 14 N‐, and 119 Sn‐NMR spectroscopy serve for following the reactions (compounds 3 to 5 ) and to characterize all final products.