Efficient synthesis of an eta2-pyridine complex and a preliminary investigation of the bound heterocycle's reactivity.

Pyridine borane is combined with TpW(NO)(PMe(3))(eta(2)-benzene) to form a complex of the heterocycle, which upon treatment with acetone and acid yields the pyridinium complex [TpW(NO)(PMe(3))(eta(2)-pyH(+))]OTf. Deprotonation in the presence of acetic anhydride delivers the N-acetylpyridinium complex as a 10:1 mixture of coordination diastereomers. This acylpyridinium resists reaction with water or oxygen but readily reacts with acetone, pyrrole, indole, or acrolein and a weak base to stereoselectively form 1,2-dihydropyridine complexes. Treatment of the indole-derived analogue with CuBr(2) results in liberation of 3-(pyridin-2-yl)-1H-indole.