Organopalladium chemistry has evolved as a powerful technique in organic synthesis. The ever coming new developments in this chemistry inspired us to develop a new synthetic approach towards the synthesis of heterocycles. In this dissertation, the syntheses of a variety of nitrogen- and oxygen-containing heterocycles were accomplished from the reactions of functionalized aryl iodides with 1,2-, 1,3-, and 1,4-dienes in the presence of catalytic amounts of palladium. It was shown that benzofuran, dibenzofuran, benzopyran, dibenzopyran, indole, tetrahydrocarbazole, tetrahydroquinoline, tetrahydro-isoquinoline, benzoxocin, and phenanthridine derivatives, as well as a variety of methylene-spiro compounds can be prepared with this methodology;The reactions with the oxygen-containing aryl iodides gave higher yields when an electron-withdrawing group was attached to the aromatic ring. With the nitrogen-containing aryl iodides better yields were obtained when an electron-withdrawing group was attached to the nitrogen atom, best yields being obtained when a tosyl group was attached to this nitrogen atom;The reactions with the 1,2-dienes were found to proceed regiospecifically for both nitrogen- and oxygen-containing aromatic substrates when five-membered rings were obtained during the cyclization step. In addition, the reactions cyclizing to a six-membered ring proved to be regiospecific, and provided as the major regioisomers products coming from attack at the less substituted carbon of the [pi]-allylpalladium intermediates;In general, the reactions were found to be regioselective providing the products coming from attack of the intermediate arylpalladium species on the less substituted carbon of the diene (except for the 1,2-dienes were all of the attacks occurred at the center carbon of the diene moiety). Best results were found to be obtained when Na[subscript]2CO[subscript]3 was used as the base and Pd(OAc)[subscript]2 as the catalyst. However in some instances, the use of Pd(dba)[subscript]2 as the catalyst, DMA as the solvent, or the addition of PPh[subscript]3 provided even better yields of products.