Claisen rearrangements—III : Convenient syntheses of the coumarins, osthenol, demethylsuberosin and Coumurrayin (cas 17245-25-9)☆

Add time:08/26/2019    Source:sciencedirect.com

A simple 3-step method for the introduction of a 3,3-dimethylallyl unit ortho to a phenolic OH group is described. 7-Hydroxycoumarin, 1, was converted to its 1,1-dimethylallyl ether, 5, by reaction with 3-chloro-3-methylbutyne followed by partial hydrogenation. Pyrolysis of 5 gave mainly the C-8 Claisen rearrangement product, osthenol, 10, and also the C-6 isomer, 14. In a similar manner, coumurrayin, 13, was prepared from 5-methoxy-7-hydroxycoumarin in 57 % overall yield.

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