Iodoenolcyclization of 2-allyl-substituted b-keto esters under thermodynamic conditions.

An improved procedure for the synthesis of diastereo-enriched tetrasubstituted 4,5-dihydrofurans by using I2-induced enolcyclization of B-keto esters is reported. The reactions using 12 in anhydrous MeCN are considered under thermodynamic control and the more stable trans isomers are preferentially produced.