吡啶4號(hào)位甲基溴代反應(yīng)問(wèn)題
請(qǐng)教一下,我在做吡啶衍生物4號(hào)位上的甲基溴代反應(yīng)(見(jiàn)圖),圖片順序可能有問(wèn)題,請(qǐng)見(jiàn)諒
1. 核磁打譜在8左右附近有清晰的二重三重峰(見(jiàn)圖),不應(yīng)該啊,請(qǐng)問(wèn)是為什么?圖是第一次的譜,4左右沒(méi)出峰,沒(méi)產(chǎn)物
2. 后來(lái)用鼓泡法(見(jiàn)圖),最后4ppm 產(chǎn)物峰出來(lái)了,但是5左右還有峰,是二溴代了嗎?而且8左右還是有二、三重峰
3. 溶劑四氯化碳用分子篩除水,1.2當(dāng)量NBS分三次加,65℃回流4h,BPO 0.12當(dāng)量,產(chǎn)率比較低,請(qǐng)問(wèn)如何改進(jìn)?
4. 過(guò)柱子純石油醚不加壓,原料點(diǎn)和產(chǎn)物點(diǎn)也不好分,雖然跑板分得很開(kāi),是因?yàn)楣枘z酸性嗎?

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P5I~23PLX%0221ESM3_Z6TE.png@liuchong630@liuchong630@yangtie2008
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首先你的原料也測(cè)試核磁了嗎?這個(gè)反應(yīng)容易出現(xiàn)2溴代物 TLC分點(diǎn)開(kāi)的話 柱層析應(yīng)該也能分開(kāi)
2溴代55%收率
Benzylic brominations with N-bromosuccinimide in (trifluoromethyl)benzene
By Suarez, Diana et al
From Synthesis, (11), 1807-1810; 2009
1溴代
Reactions of 2,6-di-tert-butylpyridine derivatives with methyl fluorosulfonate under high pressure
By Hou, C. J. and Okamoto, Yoshiyuki
From Journal of Organic Chemistry, 47(10), 1977-9; 1982
Benzylic brominations with N-bromosuccinimide in (trifluoromethyl)benzene
By Suarez, Diana et al
From Synthesis, (11), 1807-1810; 2009
Synthesis of Some Fluorinated Pyridines Using Tetrabutylammonium Fluoride
By Mobinikhaledi, A. and Foroughifar, N.
From Phosphorus, Sulfur and Silicon and the Related Elements, 181(2), 405-412; 2006
4-(Bromomethyl)-2,6-di-tert-butylpyridine (4a) A mixture of 2,6-di-tert-butyl-4-methylpyridine, 1, (0.21 g, 1.0 mmol), NBS (0.18 g, 1 mmol), and dibenzoyl peroxide (0.025 g, 1 mmol) in dry carbon tetrachloride (15 mL) was refluxed under N2 for 3 h. The mixture was then cooled in an ice bath and the precipitated succinimide was removed by filtration. The solvent was evaporated to give a brown oily mixture. This mixture was dissolved in carbon tetrachloride (15 mL). NBS (0.036 g, 0.20 mmol) and dibenzoyl peroxide (0.0050 g, 0.021 mmol) added and refluxed under N2 for another 2 h. The crude product was distilled at 90-110°C/2 mm Hg to give pure compound 4a (93%). 4-(Bromomethyl)-2,6-di-tert-butylpyridine (4a), yield 93%. 1H NMR (CDCl3): δ (ppm): 1.35 (18H, s, 2 x t-butyl), 4.38 (2H, s, CH2Br), 7.09 (2H, s, Ar). 13C NMR (CDCl3): δ (ppm): 30.1 (2 x t-butyl), 32.2 (CH2Br), 37.7 (2 x C), 115.3 (2 x CH, Ar), 145.7 (1 x C, Ar), 168.4 (2 x C, Ar),
謝謝,這幾篇我之前看了,還是用AIBN比較好
測(cè)了,但是我發(fā)現(xiàn)跑出來(lái)的兩個(gè)點(diǎn),原料和產(chǎn)物是在一起的。。。另一個(gè)就是那個(gè)芳基峰,我改用了AIBN,跑出來(lái)就一個(gè)點(diǎn)了,可能是BPO的問(wèn)題