Photocatalytic Dearomative Intermolecular Seven-Membered Ring Construction of Benzofurans

We report the synthesis of seven-membered carbocycles through the dearomative intermolecular reaction of benzofurans with vinylcyclopropanes. The significant feature of this method involves activating benzofurans through energy transfer from an activated photocatalyst. Substituent effects were investigated for each substrate, and hydrocyclohepta[b]benzofurans with a tetrasubstituted carbon were obtained as a single diastereomer. This synthetic approach compliments the reported methodologies for synthesizing this type of skeleton and introduces a new feedstock for this skeleton with a different substitution pattern. Computational studies of the reaction mechanism suggested that the reaction proceeds stepwise through addition, small ring opening, and re-cyclization. This novel synthetic approach opens up new possibilities for efficiently constructing seven-membered carbocycles. Moreover, it provides a valuable platform for discovering unique molecules with diverse substitution patterns. We report the synthesis of 7-membered carbocycles through the dearomative intermolecular reaction of benzofurans with vinylcyclopropanes. The primary feature of this process involves the activation of benzofuran through energy transfer from the activated photocatalyst. Various hydrocyclohepta[b]benzofurans with tetrasubstituted carbons were constructed as single diastereomers. Computational studies suggested that the reaction proceeds stepwise through addition, small ring opening, and re-cyclization.image

Automated summary

We report the synthesis of seven-membered carbocycles through the dearomative intermolecular reaction of benzofurans with vinylcyclopropanes. The activation of benzofurans through energy transfer from an activated photocatalyst allows for the efficient construction of hydrocyclohepta[b]benzofurans with tetrasubstituted carbons as single diastereomers. This novel synthetic approach complements existing methodologies and introduces a new feedstock for the synthesis of carbocycles with diverse substitution patterns.