Tributylstannyl pyridine

Reaction of 10-bromo-iV,l,3-trimethyl-7-oxo-2,3-dihydro-7//-pyrido [ 1,2,3-i/e]quinoxaline-6-carboxamide with 2,6-dimethyl-4-(tributylstannyl)-pyridine in the presence of (Ph3P)2Pd(II)Cl in boiling toluene gave 10-(2,6-dimethyl-4-pyridyl) derivative (OOMIPIO). 

Several different approaches have been employed to prepare pyridylstannanes, one of which involves direct metalation followed by transmetalation with RjSnCl. A regioselective metalation of 2-methoxypyridine was achieved using a mixture of bases comprised of BuLi-LiO(CH2)2NMe2 [53], Subsequent transmetalation with BujSnCl led to 2-methoxy-6-(tributylstannyl)pyridine (68), which was then coupled with pyridyl-, pyrimidyl-, and quinolinyl bromides in 31-56% yield. 

Intriguingly, the Stille coupling of quaternary pyridylstannane 12 with 2-chloropyrazine (13) proceeded to afford adduct 14 [12]. A-Methylated 3-(tributylstannyl)pyridine 12 was easily prepared by refluxing 3-(tributylstannyl)pyridine (11) with methyl tosylate in EtOAc. By contrast, only 29% yield of the coupling adduct was isolated from the Stille reaction of 3-(tributylstannyl)pyridine A-oxide and 13. 

Chloropyrazine with 3-(tributylstannyl)pyridine 1-oxide (129) gave 2-(l-oxi-dopyridin-3-yl)pyrazine (130) [Pd(PPh3)4, THF, reflux, 10 h 98% see original for procedural details].898... 

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