The Acylation of Methyl Ketones with Aliphatic Esters by Means of Sodium Amide. Synthesis of β-Diketones of the Type RCOCH2COR1
The Acylation of Methyl Ketones with Aliphatic Esters by Means of Sodium Amide. Synthesis of β-Diketones of the Type RCOCH2COR1
复制标题
DOI：
10.1021/ja01235a045
复制
发表时间：
1944-07
影响因子：
15
通讯作者：
J. T. Adams;C. Hauser
中科院分区：
文献类型：
--
作者：
J. T. Adams;C. Hauser
RCO_2C_2H_4 + CH_3COR->-RCOCH_2COR + C，H_2OH虽然用乙酸乙酯进行的乙酰化反应一般是令人满意的，但用高级脂肪酸酯进行的2-乙酰化反应以前只能得到中等产率的O-二酮。3· 4在本研究中，利用氨基钠从各种脂肪族酯和甲基酮获得了良好的O-二酮产率。在使用分子当量的正丁酸乙酯、甲基异丁基酮和氨基钠的初步实验中，当首先制备酮的钠衍生物并加入酯时，O-二酮的产率为44%，但根据更常见的实践，当将酯和酮的混合物加入到氨基钠中时，O-二酮的产率仅为36%。虽然Claisen 6报道了在苯乙酮与乙酸乙酯的乙酰化反应中，使用2当量的氨基钠与1当量的酮进行乙酰化反应，产率为77%，但后来的工作者4在脂肪酮与高级脂肪酯的酰化反应中没有使用明显过量的氨基钠，产率要低得多。我们已经发现，过量的氨基钠的存在对O-二酮的产率具有非常可抑制的影响，至少在所研究的情况下是这样。我们的结果总结在表I中。对于表中列出的前六种酯-酮组合中的每一种，使用分子当量的氨基钠和酮进行酰化，并且还使用两当量的氨基钠对一种酮进行酰化。可以看出，在额外当量的氨基钠存在下获得的产率是仅使用一当量碱获得的产率的两倍。研究了过量酯对反应的影响，
RCOaCzHt+ CHsCOR—>- RCOCH-COR+ C, hUOH While acetylations with ethyl acetate have gen-erally been satisfactory, 2acylations with higher aliphatic esters havepreviously given only fair yields of the 0-diketones. 3· 4 In the present investigation good yieldsof 0-diketones have been obtained from various aliphatic esters and methyl ketones by means of sodium amide. In preliminary experimentsusing molecular equivalents of ethyl «-butyrate, methyl isobutyl ketone and sodium amide the yield of the 0-diketone was 44% when the sodium derivative of the ketone was first prepared and the ester added, but only 36% when a mixture of the ester and ketone was added to the sodium amide in accord-ance with the more common practice. 4 The former procedure was therefore adopted, Although Claisen6 reported a 77% yield in the acetylation of acetophenone with ethyl acetate using two equivalents of sodium anude to one of the ketone, later workers4 used no appreciable excess of sodium amide in acylations of aliphatic ketones with higher aliphatic esters andobtained much lower yields. We have found that the presence of excess sodium amide has a very favor-able influence on the yield of 0-diketone, at least in the cases studied. Our results are summarized in Table I. With each of the first six ester-ketone combinations listed in the table, the acylations were carried out using molecular equivalents of sodium amide and ketone, andalso using two equivalents of sodium amide to one of the ketone. It can be seen that the yields obtained in the presence of the extra equivalent of sodium amide are twice those obtained using only an equivalent of the base. The influence of excess ester on the