Synthesis of 2(3H)-furanones via electrophilic cyclization
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The electrophilic cyclization of functionally-substituted alkynes is a very promising route to an extraordinary range of medicinally-interesting, functionally-substituted heterocycles and carbocycles. A variety of highly substituted 2(3H)-furanones are readily prepared from 3-alkynoate esters and the corresponding acids via electrophilic cyclization. This highly efficient approach proceeds under mild conditions, tolerates various functional groups, and generally provides 2(3H)-furanones in good to excellent yields. The cyclizations of 3-alkynoate esters and the corresponding acids have been performed using an excess of the electrophile at room temperature using either methylene chloride or acetonitrile as the solvent. Successful electrophiles in this process include I2, ICl, and PhSeCl. The iodine functionality introduced into the heterocycle facilitates further elaboration by Pd-catalyzed chemistry.