Efficient syntheses of benzyl andn-octyl [1,3-13C2]acetoacetates, and their application to syntheses of13C-labelled pyrrole and13C-labelled hymecromone
作者:Katsumi Iida、Kuniaki Ohtaka、Takayuki Komatsu、Tomoe Makino、Masahiro Kajiwara
DOI:10.1002/jlcr.1474
日期:2008.3.15
Benzyl [1-13C]acetate (2a) was prepared via esterification of sodium [1-13C]acetate (1) with benzyl bromide in the presence of 18-crown-6-ether in 97% yield. n-Octyl [1-13C]acetate (2b) was rapidly obtained by microwave irradiation of 1-bromooctane and potassium [1-13C]acetate (obtained by salt exchange of 1) absorbed on Al2O3 in 82% yield. Solvent-free Claisen condensation of benzyl or n-octyl [1-13C]acetate (2a or 2b) in the presence of potassium tert-butoxide efficiently gave benzyl or n-octyl [1,3-13C2]acetoacetate (3a or 3b) in 51 or 68% yield, respectively. Dibenzyl 2,4-dimethyl[2,4-13C2]pyrrole-3,5-di[13C]carboxylate (4) was synthesized from benzyl [1,3-13C2]acetoacetate (3a) in 54% yield. [2,4-13C2]Hymecromone (6) (7-hydroxy-4-methyl[2,4-13C2]coumarin) was obtained from n-octyl [1,3-13C2]acetoacetate (3b) and 1,3-benzenediol (5) in 73% yield. Copyright © 2008 John Wiley & Sons, Ltd.
苯基[1-13C]醋酸乙酯(2a)通过用溴苄在18-冠-6醚存在下对钠[1-13C]醋酸盐(1)进行酯化反应制备,产率为97%。n-辛基[1-13C]醋酸乙酯(2b)通过微波辐照1-溴辛烷和钾[1-13C]醋酸盐(由1进行盐交换获得)在Al2O3上快速获得,产率为82%。在存在叔丁氧钾的条件下,无溶剂Claisen缩合苯基或n-辛基[1-13C]醋酸乙酯(2a或2b)高效生成苯基或n-辛基[1,3-13C2]乙酰乙酸酯(3a或3b),产率分别为51%或68%。双苄基2,4-二甲基[2,4-13C2]吡咯-3,5-二[13C]羧酸盐(4)以54%的产率由苯基[1,3-13C2]乙酰乙酸酯(3a)合成。 [2,4-13C2]氢美克罗酮(6)(7-羟基-4-甲基[2,4-13C2]香豆素)由n-辛基[1,3-13C2]乙酰乙酸酯(3b)和1,3-苯二醇(5)以73%的产率获得。版权所有©2008 John Wiley & Sons, Ltd.