A general synthesis of 3-chalcogen benzo[b]furans from the readily available 2-alkynylanisoles, via FeCl(3)/diorganyl dichalcogenides intramolecular cyclization, has been developed. Aryl and alkyl groups directly bonded to the chalcogen atom were used as cycling agents. The results revealed that the reaction significantly depends on the electronic effects of substituents in the aromatic ring bonded to the selenium atom of the diselenide species. We observed that the pathway of reaction was not sensitive to the nature of substituents in the aromatic ring of anisole since both the electron-donating and the electron-withdrawing groups delivered the products in similar yields. In addition, the obtained heterocycles were readily transformed to more complex products by using a chalcogen/lithium exchange reaction with n-BuLi followed by trapping of the lithium intermediate with aldehydes, furnishing the desired secondary alcohols in good yields.

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We present here the reaction of unsymmetrical diorganoyl dichalcogenides (RSe−SR1) with terminal alkynes under catalyst-free conditions, by a one-pot procedure, to prepare bis- and tris-chalcogenide alkenes selectively, avoiding the previous preparation of chalcogen alkynes. The reaction proceeded cleanly under mild reaction conditions, and the addition of unsymmetrical dichalcogenides to alkynes occurred stereoselectively to give exclusively the corresponding Z isomers.

The synthesis of various Z-enynols via reaction of vinyllithium intermediate with aldehydes and ketones is described. The subsequent cyclization of a wide variety of Z-enynols afforded substituted furans and dihydrofurans with high regioselectivity under mild reaction conditions.