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Euparin ( I ) , dehydrotremetone (2). and methoxyeuparin (3) have been synthesized by a short procedure involving the reaction of copper( I) isopropenylacetylide with an appropriate p-acetyl-o-halogenophenol.SEVERAL classes of natural products can be regarded as acetophenone derivatives bearing an isopentenyl residue either as a side-chain or as part of a heterocycle, and biogenetic relationships between them have been discussed.l One such class is based on the 5-acetyl-2-isopropenylbenzofuran framework and is exemplified by euparin (1) , dehydrotremetone (2), and methoxyeuparinWe have recently synthesized some natural norlignans with 5-alkyl-2-arylbenzofuran structures 2 and have since sought to determine if the acetophenone products were amenable to synthesis by the same gener a1 pathway of benzofuran construction 3-6 by reaction of an o-halogenophenol with copper( I) isopropenylacetylide.(3). Euparin, a yellow constituent ofEupatorium Purpureum (gravel root) has been known since 1890,' and its structure (1) was established by Robertson 8 in 1939. It has since been isolated from other Eupntorium species (E. cannabinum and E. japonica lo), from Encelia californica,ll and from A brotafiella nivigena,l2 and its