The selectivity on the oxidation by cytochrome P450 is probably due to appropriate arrangement of a substrate near the active intermediate of an enzyme by molecular recognition. We have found that ruthenium (Ru) porphyrin–pyridine N-oxide system is an exceptionally potent and efficient oxidizing one for unactivated alkanes, and so on. Ru porphyrin with substrate-recognition sites (1) is expected to be superior to simple Ru porphyrin in both selectivity and efficiency. 1H-NMR study showed that substrate 2 (tetradecane form), 3 (dodecane form) well makes 1:1 complex with 1 by multiple hydrogen bonding. By the addition of 2,6-dichloropyridine N-oxide, 2, 3 was oxidized with high regio-selectivity. On the other hand, Ru porphyrin without recognition sites gave no product. These results provide evidence that substrate recognition by a catalyst is advantageous for high regio-selectivity and high reactivity.
