Zum Mechanismus der Carbodesilylierung 4‐ bzw. 5‐substituierter 2‐(Trimethylsilyl)pyridine mit Benzaldehyd

Synthesis of Differently Disubstituted 2,2′‐Bipyridines by a Modified Negishi Cross‐Coupling Reaction

“…This sequence was especially advantageous not only because of the high yields but also because of the ease of preparation, since none of these steps requires tedious purification procedures such as column chromatography, and the resulting 2‐amino‐5‐methoxypyridine ( 6 ) could easily be isolated by distillation. The subsequent Sandmeyer halogenations could be performed through known or slightly modified procedures 22…”

“…2‐Amino‐5‐methoxypyridine (6): 22 A mixture of 1‐(5‐methoxypyridin‐2‐yl)‐2,5‐dimethyl‐1 H ‐pyrrole ( 8 , 3.5 g, 17.3 mmol), hydroxylamine hydrochloride (12.02 g, 173 mmol), triethylamine (4.8 mL, 34.6 mmol), ethanol (30 mL), and water (15 mL) was heated at reflux for 20 h. The cooled solution was quenched with cold HCl (50 mL), washed with diisopropyl ether, and the pH was adjusted to 9−10 with 6 n NaOH. The resulting mixture was extracted several times with dichloromethane.…”

“…2‐Chloro‐5‐methoxypyridine (7): 22 2‐Amino‐5‐methoxypyridine ( 6 , 895 mg, 7.2 mmol) was dissolved in concd. HCl (20 mL) and the system was cooled to ca.…”

5,5″-Disubstituted 2,2′:6′,2″-Terpyridines through and for Metal-Mediated Cross-Coupling Chemistry

“…The presence of free alkoxide otherwise led to an effective competition for the nucleophiles by the reactive C-2 position of 1 d. The tin component 2 b, prepared by electrophilic stannylation via the corresponding bromochloropyridine (2 a), was lithiated at C-2. [13,14] The coupling between the central pyridines 1 a and 1 e and tin compound 2 b was achieved by the normal Stille procedure with 4 mol % of Pd[(PPh 3 ) 4 ]. [15] The central pyridines 4 e and 4 f with two TMSn groups were synthesized by nucleophilic stannylation (Scheme 2) in analogy to the known synthesis of 4 a.…”

“…Compounds 1 c [11] and 1 d [12] are known, but were prepared alternatively. Compounds 1 b, [10] 2 a, [13] 4 a, [16] and 11 [24] were prepared according to the literature. For compounds 2 b and 7, see references [14] and [19].…”