We report here the results of synthetic organic reactions which proceed under mild conditions through the formation of cationic halocyclization intermediates. In the presence of I2 and collidine or lutidine, α-iodination reactions of unsaturated carboxamides and N-allylic carboxamides proceed in good yields through the activation of α-hydrogens by the formation of cyclic iminium ethers (iodolactonization intermediates). The iodine-mediated method can be also applied to the activation of enamide derivatives; that is, in the presence of I2, the Diels-Alder reactions of N-allylic enamides which are unreactive dienophiles, proceed in good yield through the formation of the cyclic iminium ether. These activation processes are successfully extended to asymmetric α-iodination of unsaturated carboxamides having homochiral 2,5-disubstituted pyrrolidine and asymmetric Diels-Alder reaction using novel axially chiral N-acryl anilide. Furthermore, the reactions of p-methoxybenzyl pentenyl ether with NIS and O-pentenyl oxime with NBS resulted in the activation of C-O bond and N-O bond through the formation of cationic haloetherification intermediates, and the following reaction with alchols and migration of anti-substituent gave p-methoxybenzylation and Beckmann rearrangement products in good yields, respectively.
|ジャーナル||Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry|
|出版ステータス||Published - 1998|
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