The N-hydroxyphthalimide derivatives, F15- and F17-NHPI, bearing a long fluorinated alkyl chain, were prepared and their catalytic performances were compared with that of the parent compound, N-hydroxyphthalimide (NHPI). The oxidation of cyclohexane under 10 atm of air in the presence of fluorinated F15- or F17-NHPI, cobalt diacetate [Co(OAc)2], and manganese diacetate [Mn(OAc)2] without any solvent at 100 °C afforded a mixture of cyclohexanol and cyclohexanone (K/A oil) as major products along with a small amount of adipic acid. It was found that F15- and F17-NHPI exhibit higher catalytic activity than NHPI for the oxidation of cyclohexane without a solvent. However, for the oxidation in acetic acid all of these catalysts afforded adipic acid as a major product in good yield and the catalytic activity of NHPI in acetic acid was almost the same as those of F15- and F17-NHPI. The oxidation by F15- and F17-NHPI catalysts in trifluorotoluene afforded K/A oil in high selectivity with little formation of adipic acid, while NHPI was a poor catalyst under these conditions, forming K/A oil as well as adipic acid in very low yields. The oxidation in trifluorotoluene by F15- and F17-NHPI catalysts was considerably accelerated by the addition of a small amount of zirconium(IV) acetylacetonate [Zr(acac)4] to the present catalytic system to afford selectively K/A oil, but no such effect was observed in the NHPI-catalyzed oxidation in trifluorotoluene.
Tributyltin hydride-mediated radical reactions of organic halides were successfully carried out in a continuous flow system using a microreactor. The reactions proceeded within a very short period of time, coupled with quickly decomposing radical initiators such as V-65 and V-70. The continuous flow reaction system was applied to gram scale synthesis of a key intermediate for furofuran lignans.
Tin-free Giese reaction and the related radical carbonylation process proceeded efficiently in the presence of sodium cyanoborohydride and tetrabutylammonium cyanoborohydride. The reaction took place chemoselectively at the carbon−iodine bond but not at the carbon−bromine and carbon−chlorine bonds. The iodine atom transfer followed by hydride reduction of the resulting carbon−iodine bond is proposed as a possible mechanism.
THP (tetrahydropyran) has been found to show an excellent stability towards autooxidation, compared with THF. Tributyltin hydride mediated radical cyclization, when conducted in THF as a solvent, suffers from competition of hydrogen abstraction from the solvent, whereas the use of THP resulted in the course to negligible degree. Tributyltin hydride, TTMSS, and hexanethiol mediated radical reactions were carried out successfully using THP as a solvent.
Phase-vanishing (PV) method using perfluorohexanes as a screen phase was applied to cyclopropanation reactions with CH2I2/Et2Zn and CH2I2/Et3Al. When Et3Al was used as a carbenoid generator, the reaction proceeded smoothly and desired cyclopropane derivatives were obtained in high yield. The PV cyclopropanation took 2 or 3 days to complete, however, reduction of reaction time by a factor of 2–3 was also achieved by vigorous stirring after the bottom CH2I2 layer disappeared.
An efficient cross-addition reaction of dienes with aldehydes was developped by using RuHCl(CO)(PPh3)3 as a catalyst to give a wide variety of β,γ-unsaturated ketones, where a π-allylruthenium species, derived from hydroruthenation of diene, may be involved as a key intermediate.