Trifluoroacetic anhydride mediated benzoylation; Methyl 2-(2,3,5-Trimethoxy-4-methylbenzoyl)benzoate
SyntheticPage 441
DOI:
10.1039/SP441
Submitted Jul 20, 2010, published Jul 21, 2010
Christopher Cooksey (
rsc@chriscooksey.demon.co.uk)
A contribution from
R J H Clark Group, UCL
Chemicals Used
phthalic acid monomethyl ester page 428
2,3,6-trimethoxyltoluene page 426
trifluoroacetic anhydride (Aldrich)
Procedure
Trifluoroacetic anhydride (6 cm3, 43 mmol) was added to phthalic acid monomethyl ester (1.8 g, 10 mmol) which dissolved in 1 m. After 5 m a solution of 2,3,6-trimethoxyltoluene (1.8 g, 10 mmol) in CH2Cl2 (6 cm3) was added dropwise over 5 m at 25 ºC. After 6 h the solvents were evaporated to give a dark green oil. Recrystallisation from cyclohexane (70 cm3) gave white crystals (1.97 g) and a further amount (0.28 g, a total yield of 81%) after reducing the volume to 25 cm3.
Author's Comments
Trifluoroacetic anhydride mediated coupling of
methyl 3-methoxyphthalate with
2,6-dimethoxytoluene reportedly gives 84% yield of the substituted benzoyl benzoate (R D Gleim, S Trenbeath, F Suzuki and C J Sih, Chem Comm 1978, 242b-244,
doi: 10.1039/C3978000242b). On a larger scale using 7.09 g of trimethoxytoluene a yield of 75% was obtained. A similar reaction of
1,2,4-trimethoxybenzene with
methyl phthalate at 25 – 30 ºC for 45 m gave mainly the required product with 20% of the corresponding phthalide (G Bargellini, Gazz. Chim. Ital. 1914, 44, 193-200).
Data
The product had a m.p. 117.8 ºC
δH (CDCl3) 7.90dd (1.8, 7.4), 7.54td, 7.49td, 7.40dd (1.8, 7.0), 7.22s, 3.85s, 3.84s, 3.70s, 3.27s, 2.14s
δ
C (CDCl
3) 195.16, 167.31, 153.52, 152.30, 148.99, 143.51, 131.41, 129.65, 129.41, 129.41, 127.72, 126.27, 126.12, 111.07, 61.31, 60.26, 55.88, 52.22, 9.56.
Lead Reference
R D Gleim, S Trenbeath, F Suzuki and C J Sih, Chem Comm 1978, 242b-244,
doi: 10.1039/C3978000242b.
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Keywords: benzoylation, esters, ketones