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Efficient syntheses of benzyl and n-octyl [1,3-13C2]acetoacetates, and their application to syntheses of 13C-labelled pyrrole and 13C-labelled hymecromone

✍ Scribed by Katsumi Iida; Kuniaki Ohtaka; Takayuki Komatsu; Tomoe Makino; Masahiro Kajiwara

Publisher
John Wiley and Sons
Year
2008
Tongue
French
Weight
95 KB
Volume
51
Category
Article
ISSN
0022-2135

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✦ Synopsis

Benzyl [1-13 C]acetate (2a) was prepared via esterification of sodium [1-13 C]acetate (1) with benzyl bromide in the presence of 18-crown-6-ether in 97% yield. n-Octyl [1-13 C]acetate (2b) was rapidly obtained by microwave irradiation of 1-bromooctane and potassium [1-13 C]acetate (obtained by salt exchange of 1) absorbed on Al 2 O 3 in 82% yield. Solventfree Claisen condensation of benzyl or n-octyl [1-13 C]acetate (2a or 2b) in the presence of potassium tert-butoxide efficiently gave benzyl or n-octyl [1,3-13 C 2 ]acetoacetate (3a or 3b) in 51 or 68% yield, respectively. Dibenzyl 2,4-dimethyl[2,4-13 C 2 ]pyrrole-3,5-di[ 13 C]carboxylate (4) was synthesized from benzyl [1,3-13 C 2 ]acetoacetate (3a) in 54% yield. [2,[4][5][6][7][8][9][10][11][12][13] C 2 ]Hymecromone (6) (7-hydroxy-4-methyl[2,4-13 C 2 ]coumarin) was obtained from n-octyl [1,3-13 C 2 ]acetoacetate (3b) and 1,3-benzenediol (5) in 73% yield.

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