n-BuLi; TMEDA in tetrahydrofuran addn. of BuLi to mixt. of pyridine derivative and TMEDA at 195-208 K, stirring (263 K, 2 h), dropwise addn. of Sn-compd. at 195-208 K; quenching with H2O, extn. into ether, drying of org. layer (MgSO4), chromy. (SiO2), crystn. (hexane/EtOAc=1:1); can be recrystallized;