エナミド閉環反応と複素環合成

抄録

N-α, β-Unsaturated acylenamines and N-α, β-unsaturated acylanilides, which form a common conjugated six π electron system, are two major types of enamides capable of undergoing smooth cyclization under both photochemical and thermal conditions according to the Woodward-Hoffmann rule. These cyclizations of enamides are found to occur under various conditions, such as nonoxidative (in the absence of oxygen), oxidative (in the presence of oxidizing agent), reductive (in the presence of hydride reagent), and even under asymmetric conditions (under asymmetric circumstance), thus established the enamide cyclization as a useful synthetic weapon widely applicable to the construction of nitrogen-containing heterocyclic compounds, particularly related to alkaloids. Usefulness of this enamide cyclization is proved by the establishment of stereochemical and regiochemical controls of the cyclization by the use of substituent and solvent effects. This review covers rather quick look at the outline of this enamide cyclization and its application to the synthesis of heterocycles.