卡宾引发剂
氮杂环卡宾(NHC)在过去的几十年里得到了相当的重视。它作为配体和催化剂广泛的应用在有机转换中。在市售催化量的NHC存在的温和条件下，烯醇化以及非烯醇化的醛，羰基酯与Ruppert-Prakash试剂作用生成三氟甲基化产物。但是低活性的酮并不发生反应，所以该方法可用于醛和酮的选择性三氟甲基化1。
示例：
To 2,2-dimethyl-4-pentenal(1.36 mL, 10.0 mmol) in a dry flask under N2 were added DMF(anhydrous, 10 mL), TMSCF3 (4.2 g, 30 mmol), and carbine 9 (34 mg, 0.10 mmol).The mixture was stirred at room temperature for 4 h. HCl solution (2 N, 12 mL) was added and the solution was stirred at room temperature until all TMS protected intermediate converted to product. Water (60 mL) was added and the aqueous layer was extracted with ether (3×40 mL). Organic layers were combined and washed with saturated NaHCO3 aqueous solution (30 mL), brine (30mL), dried over MgSO4. Solvents were removed under vacuum to give the crude residue, which was purified by silica flash chromatography (10% Et2O/pentane) to give 1.29 g product (71% yield).
三苯基膦引发
三苯基膦是一种广泛与Me3SiCF3使用的三氟甲基化反应的催化剂。但是一般产率偏低并且反应时间较长，这可能归因于三苯基膦较弱的亲核性2。最近，Shibata研究出在DMF中使用催化量的三叔丁基膦可以适用于高效的路易斯碱催化的多种醛和酮的亲核三氟甲基化3。
反应实例：
Typical Experimental Procedure.
Tri-tert-butylphosphine [P(t-Bu)3,3.9 mg, 0.019 mmol]) was placed in a round-bottomed flask under N2. Dry DMF (0.25 mL) and aldehyde (0.19 mmol) were added. To the stirred solution, Me3SiCF3 (57 μL, 0.38 mmol) was added at r.t. The mixture was stirred at r.t. for 0.5 h; the reaction was concentrated under reduced pressure. The residue was chromatographed on silica gel using hexane to afford product.
【参考文献】
1.Song, J. J.; Tan, Z.; Reeves, J. T.; Gallou, F.; Yee, N. K.; Senanayake, C.H. Org. Lett. 2005, 7, 2193-2196.
2.(a) Kim, J.; Shreeve, J. M. Org. Biomol. Chem. 2004, 2,2728-2734.
(b) Hagiwara, T.; Kobayashi, T.; Fuchikami,T. Main Group Chem. 1997, 2, 13-15.
3. Mizuta, S.; Shibata, N.; Sato, T.; Fujimoto, H.; Nakamura, S.; Toru, T. Synlett 2006, 2, 267-270.
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