Summary
Claisen migrations of the allyl ether of 4∶7-dimethyl-5-hydroxy-coumarin gives rise to three isomeric compounds depending upon the conditions, (I) 6-allyl-5-hydroxy-4∶7-dimethyl coumarin (high yield), (II) the corresponding chroman (high yield), and (III) 8-allyl-5-hydroxy-4∶7-dimethyl coumarin (low yield). (II) has been shown to be a chroman by comparison with the corresponding methyl coumaran obtained by authentic methods from (I). The acetate of the above coumarin undergoes Fries reaction to give the 6-acetyl compound. Claisen migrations of the allyl ether of 7-hydroxy-5-methyl-coumarin yields only the 8-allyl-derivative. The difference in the behaviour of the derivatives of 5- and 7-hydroxy coumarins and the special conditions of the chroman and coumaran ring closure ofo-allyl phenols are discussed.
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Krishnaswamy, B., Rao, K.R. & Seshadri, T.R. Synthetic experiments in the benzo-pyrone series. Proc. Indian Acad. Sci. (Math. Sci.) 19, 5 (1944). https://doi.org/10.1007/BF03174811
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DOI: https://doi.org/10.1007/BF03174811