2位吧，電子云密度低一些，有利于親核反應(yīng)（個(gè)人觀點(diǎn)）

2位
99 % Stage 1: With n-butyllithium in tetrahydrofuran
Stage 2: in tetrahydrofuran, T= -5 °C
Nurkkala, Lasse J.; Steen, Robert O.; Dunne, Simon J.; Synthesis; nb. 8; (2006); p. 1295 - 1300; Art.No: T12905SS

To a stirred solution of 15,6 g (0.10 mol) of 2-(3-thienyl)-1,3-dioxolane in 100 ml of anhydrous ether, n-butyl-lithium
(1.48N, in hexane, 74.3 ml) is added dropwise under nitrogen at room temperature.
After being refluxed for 15 minutes, the reaction mixture is cooled to -78.deg. C. and tri-n-butyltin chloride (34.18 g,
0.105 mol) in 100 ml of dry tetrahydrofuran is added dropwise.
After the addition is complete, the mixture is warmed to room temperature and the solvent evaporated.
To the oily residue 100 ml of hexane is added, and the resulting precipitate (LiCl) is filtered off.
The filtrate is evaporated and the residue distilled at reduced pressure, giving 34.16 g (77percent) of the desired product.
With n-butyllithium in tetrahydrofuran, hexane
Patent; American Cyanamid Company; US5869483; (1999); (A1) English，