Abstract
Allyloxycoumarins (3,4) and ethyl 2-allyloxycinnamates (27, 28) were converted into 7-hydroxy-8- allylcoumarins (5,6), 2-hydroxy-3-allyl-4-methoxy-E-cinnamate ester (29), and 2-hydroxy-3-acetyl-4-methoxy-5-allyl cinnamate ester (30) by thermal Claisen rearrangement. The compounds 7-hydroxy-8-allylcoumarins (5,6) and 2-hydroxy-3- allyl cinnamate (30) on acylation or benzoylation, followed by Fries rearrangement gave 6-acetyl-7-hydroxy-8-allylcoumarins (15-20), 6-benzoyl-7-hydroxy-8-allylcoumarins (21,22), and 2-hydroxy-3-allyl-4-methoxy-5-acetylcoumarin (31). The compounds (33) and (30) underwent cyclization using boron tribromide in dichloromethane solvent at 0 degree C temperature to give 6-acetyl-7-hydroxy-8-allylcoumarin (15 or 34), that is, starting compound and 6-allyl-7-hydroxy-8-acetyl coumarin (32).. KEYWORDS :Allyl cinnamate, Coumarin, Claisen rearrangement, Regioselectivity.
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