(4+3)-cycloaddition chemists of oxidopyridinium ions and related study
The (4+3)-cycloaddition reaction is a cycloaddition between a 4-atom species and a 3-atom species to form a seven-membered ring. This reaction results in the formation of seven-membered rings. Our research expanded the scope of (4+3)-cycloaddition reaction by using the oxidopyridinium species as the dienophile -- the 3-atom species. By adding an electron-withdrawing functional group to the starting material, we were be able to get good to excellent product yield. The process provides rapid access to bicyclic nitrogenous structures resembling natural alkaloids. [2+2]-Photocycloaddition is a cycloaddition between two olefins to form a cyclobutane ring. The intramolecular [2+2]-cycloaddition of nitrogen-substituted alkenes can be employed to make complicated alkaloids. Our previous work made the 7-azabicyclo[4.3.1]deca-3,8-diene skeleton, which is a nice substrate for the cycloaddition. Under UV radiation, the heteroatom-substituted unsaturated ester undergoes intramolecular [2+2]-cycloaddition with the cyclic alkene to make a cage-like ketone in good to excellent yield, giving rise to a rigid tropane-like alkaloid skeleton. The scope and mechanism of the photochemical reaction will be discussed.
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