现代有机合成试剂(5):金属盐和有机金属试剂

三氧化硫对碳－金属键的插入反应，提供了由芳卤或烯卤制备磺酸的又一条途径。有机锂是较为典型的试剂。由于三氧化硫在操作中较为不便，而使用三氧化硫－吡啶或三氧化硫－三甲胺复合试剂能使反应在更为温和，便利的条件下进行。

以三氧化硫－三甲胺复合物为起始剂，在无水乙醚或四氢呋喃中与有机锂化合物反应，控制反应温度由－78℃到室温，得到磺酸盐，酸化后即得磺酸。

【Smith K, Hou D., J. Org. Chem. 1996, 61, 1530】

To 4-bromotoluene (518 mg, 3.1 mmol) was added n-BuLi(2.3 M in hexane, 1.35mL, 3 mmol) over 10 min with cooling (ice bath). After 6 hours, the supernatantsolution used in the next stage. To a stirred suspension of crystalline STTAC(sulfur trioxide-trimethylamine complex, commercially available) (431 mg, 3.1mmol) in dry THF (15 mL) at –78 oC was added the preformed hexanesolution of p-tolyllithium dropwise over 15 min. The reaction mixturewas stirred for 2 hours at – 78 oC and then allowed to warm to roomtemperature over 18 hours. After removal of solvent, H2O (10 mL) andKOH (3M, 1 mL, 3 mmol) wereadded to the mixture, which was then extracted with Et2O to removeunreacted 4-bromotoluene. The aqueous solution was evaporated to a white solid.HCl(6 M, 4 mL, 24 mmol) wasadded. The mixture was extracted with EtOAc (4×20 mL), and the combined organicextract was dried (MgSO4) and evaporated to give a moist solid. Et2O(15 mL) was added and some white solid precipitated. This was washed withfurther Et2O (2×10 mL). The combined Et2O extracts wereconcentrated to give white crystals (383 mg, 62%) of the monohydrate.

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