Copper-Catalyzed Cyclopropanation of α-Diazoketones to Norcaradienes

Reisman et al. have reported a copper-catalyzed intramolecular arene cyclopropanation of α-diazoketones to provide the norcaradienes. In the catalyst screening, relatively electron-poor Cu(II) salts, such as Cu(hfacac)₂ and Cu(tfacac)₂, gave good results. Furthermore, they have applied the cyclopropanation to an enantioselective total synthesis of diterpenoid (+)-salvileucalin B. Its cytotoxicity against A549 and HT-29 human adenocarcinoma cells has been reported.