n-butyllithium in tetrahydrofuran byproducts: Sn(n-Bu)4; disoln. of stannyl silyl ether in dry THF, cooling to -78°C (under Ar), dropwise addn. of n-BuLi in hexane (3 equiv.) (via syringe), stirring (-78°C, 15 min)quenching by rapid addn. of water at -78°C; warming to room temp., extn. with petroleum ether, flash chromy., eluation of tetraalkylstannane with hexane, eluation of product with ethyl acetate/hexane;