Regio- and Stereoselective, Intramolecular [2+2] Cycloaddition of Allenes, Promoted by Visible Light Photocatalysis

Enallenylamides have been utilized for the synthesis of heterobicycle[4.2.0]octane derivatives via Ir/h & nu; promoted [2+2] cycloaddition reaction. The reaction specifically targets the distal double bond of the allene moiety, and results in the exclusive formation of the trans product. The process is conducted at room temperature and under an inert atmosphere. An extensive study on the substituent propensities during the cycloaddition step revealed variable effects. Electron-withdrawing groups conjugated with the double bond participating in the cycloaddition either hindered the process or reduced its yield. Conversely, electron-donating substituents enhanced the efficiency, resulting in product yields ranging from 60% to 88%. Our study also demonstrated the influence of protecting groups on the reaction pathway.

Automated summary

Enallenylamides are used for the synthesis of heterobicycle[4.2.0]octane derivatives through Ir/h & nu; promoted [2+2] cycloaddition reaction. This reaction targets the distal double bond of the allene moiety, leading to the exclusive formation of trans product. The process is conducted at room temperature and under an inert atmosphere. A study on the substituent propensities reveals variable effects, with electron-withdrawing groups hindering the process or reducing its yield, while electron-donating substituents enhancing the efficiency with yields ranging from 60% to 88%. The influence of protecting groups on the reaction pathway is also demonstrated.