Dehydrogenation Reaction of Cycloalkanones Catalyzed by Palladium Nitrafe-Phosphine and -Sulfide Systems

다국어 초록 (Multilingual Abstract)

Activation of the aliphatic carbon-hydrogen bond was investigated in the dehydrogenation reaction of cycloalkanone (1-cyclopentanone, 1-cyclohexanone) using Pd(NO₃)₂-PR₃ (PR₃= PPh₃, P(p-C_6H₄CH₃)₃, P(p-C_6H₄-OCH₃)₃, P(p-C_6H₄F)₃) and Pd(NO₃)₂-SR₂ catalytic systems (SR₂=SPh₂, S(CH₂Ph)₂, S(CH₂CH₂CH₃)₃, S[C(CH₃)₃]₂, S[CH(CH₃)₂]₂, S[(CH₃)CH(C₂H_5)]₂). The reaction of cyclic ketones was carried out for 1.5 h in the presence of Pd(NO₃)₂ with phosphine or sulfide at 75℃. The molar ratio of Pd(N0₃)₂ to PPh₃ providing the highest yield was 1:3 and this ratio was maintained for the other phosphines and sulfides used in this work. The yield of 2-cyclohexen-1-one decreased as the basicity of the substituent on the phosphorus decreased; P(p-C_6H₄CH₃)₃> P(p-C_6H₄OCH₃)₃ > P(C_6H_5)₃ > P(p-C_6H₄F)₃> none. For sulfides, a similar trend was observed except for the lower yield than for phosphines with the same substituent; S[CH(CH₃)₂]₂>S[(CH₃)CH(C₂H_5)]₂>S(CH₂CH₂CH₃)₂>S(C_6H_5)₂>S(CH₂C_6H_5)₂∼S[C(CH₃)₃]₂. In the case of 2-cyclopenten-1-one, the order of the yield for the phoshine ligand indicated that the reaction proceeded in the same manner as in the case of 2-cyclohexen-l-one; P(p-C_6H₄CH₃)₃ > P(C_6H_5)₃ >none > P(p-C-6H₄F)₃. However, the reaction seemed to proceed with a different mechanism for the sulfide ligand considering the different order of the yield; S(C_6H_5)₂ > S(CH₂C_6H_5)₂ = S[(CH₃)CH(C₂H_5)₂ > S[CH(CH₃)₂]₂ > S(CH₂CH₂CH₃)₂.