Synthesis of heterocycles by iodocyclization and controlling of aromatization

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Iodocyclization is one of the most attractive methods for the construction of functionalized molecular architecture. This reaction can create not only the ring skeleton but also the iodo functionality for further transformation. In addition, iodinating reagents are relatively inexpensive and are ideal for achieving environmentally friendly reactions. I have developed a new method of iodocyclization based on reagent-controlled oxidative aromatization. This strategy takes advantage of the dual nature of iodine as both an iodinating and an oxidizing agent. The revealed approach enabled "product switch"and enhanced the flexibility of the synthetic pathway toward pyrazoles, isoxazoles, and pyrolles. In addition, the iodo moiety of the cyclized product could create further diversity. The utility of this methodology was demonstrated in the synthesis of valdecoxib and its 2, 5-dihydro analogs. During the elaborating process, fortunately, an efficient approach to benzoxazoles via tandem migration-carboalkoxylation of o-isocyanophenyl acetals has been developed.