Intramolecular cyclopropanation of alkenyl α-diazoacetates and alkenyl diazomethyl ketones was examined by using optically active (ON+) Ru (II)(salen) and Co (II)(salen) complexes as catalysts. For the cyclization of 2-alkenyl α-diazoacetates, Co (II)(salen) complexes 9 and 10 were found to be superior catalysts to the corresponding (ON+) Ru (II)(salen) complexes 4 and 5. On the other hand,(ON+) Ru (II)(salen) complex 2 was ...