简单利用芳香醛和脂肪醛酮制备芳基酮的方法

2014年Daniel M. Allwood等人报道了芳香醛和Ts腙在碱性条件下反应制备芳基烷基酮的方法【Org. Lett. 2014, 16, 3064-3067】。从脂肪醛酮出发，醛酮和TsNHNH2按1：1当量在甲醇中反应得到腙，浓缩后无需纯化直接用于下一步，加入碳酸铯，在二氧六环中 110℃封管反应，可以得到相应的芳基烷基酮。此方法避免了Roskamp反应中各种危险的重氮化合物的制备，使这样转变方法更加安全，易于操作。

此方法对于两种底物都有很好的普适性。常见的苯甲醛或杂芳基甲醛与脂肪醛酮都可以高产率的进行反应。

反应机理

操作步骤

General Procedure A:

To a solution of tosylhydrazide (1.0 equiv.) in MeOH (0.5 M) was added aldehyde/ketone (1.0 equiv.). The reaction mixture was stirred at room temperature until complete conversion was observed by TLC. Solvents were removed in vacuo to give the Tosylhydrazone compound.

General Procedure B:

Tosylhydrazone (0.5 mmol, 1.0 equiv.), Cs₂CO₃ (0.75 mmol, 1.5 equiv.) and aldehyde (if a solid at room temperature, 0.5 mmol, 1.0 equiv.) were placed in a tube. The tube was backfilled with argon and evacuated (3 cycles), before addition of 1,4-dioxane (2 mL) under an argon atmosphere, followed by addition of aldehyde (if a liquid at room temperature, 0.5 mmol, 1.0 equiv.). The tube was sealed with a silicone/PTFE cap and heated to 110 °C for 6 h. The mixture was cooled to room temperature, quenched with NH₄Cl (2 mL, saturated aqueous solution) and extracted with CH₂Cl₂ (3 × 2 mL). The combined organic phases were dried over MgSO₄ and solvents removed in vacuo to give a residue which was purified by flash column chromatography (EtOAc/hexane) to give the title compounds.

参考资料

Org. Lett. 2014, 16, 11, 3064–3067