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20.6.1.4.6 Variation 6: Using Other Benzoic Acid Anhydrides

DOI: 10.1055/sos-SD-020-01369

Maier, M. E.Science of Synthesis, (2007201465.

While the Yamaguchi lactonization is a quite reliable method and has broad scope, it is a stepwise operation. Thus, prior to the lactonization step the ω-hydroxy acid has to be converted into the mixed anhydride with the benzoyl chloride in presence of triethylamine. Using substituted benzoic anhydrides instead, a variety of lactones can be prepared in high yields at room temperature from the corresponding ω-hydroxy acids in the presence of base.[‌207‌] In one variation, the ω-hydroxy acid is treated with 2-methyl-6-nitrobenzoic anhydride (144) in the presence of 4-(dimethylamino)pyridine in dichloromethane at room temperature, resulting in good yields for the corresponding lactones. Some results are shown in Scheme 62.

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