Metal nanoparticles as heterogeneous catalysts have been limited to serve low-valent metal surfaces, although high-valent metal chemistry covers a wide range of homogeneous catalytic reactions. We reported that high-valent Pd(IV) clusters efficiently promotes directed C-H halogenation reactions. In addition, Pd nanoparticles by the adjustment of oxidation states provide both high-valent Pd(IV) and low-valent Pd(0) species within one system, and thus a tandem reaction of C-H halogenation and cross coupling such as C-N, C-C, and C-S bond formation is successfully established.
[$Rh(III)Cp^\ast$]-catalyzed directed C-H bromination and iodination reaction of 2-aryl isoquinolines/pyridines is highly efficient to provide atropisomeric biaryl compounds. Among several reported C-H bond halogenation methods, the combination of [$Rh(III)Cp^\ast Cl_2]_Cl2/AgSbF_6$, N-halosuccinimide, and pivalic acid in 1,2-dichloroethane is found to be the only effective catalytic system to provide atropisomeric 2’-halogenated 2-aryl isoquinolines/pyridines.
We have demonstrated that the directed C-H hydroxylation and arylation reaction catalyzed by [$Rh(III)Cp\ast Cl_2]_2/AgF$ is highly efficient to provide hydroxylated aromatics (phenols) and atropisomeric biaryl compounds. This transformation is successfully applied for C-H hydroxylation by $H_2O$ and C-H arylation by $PhI(OPiv)_2$ to provide excellent reactivity and broad substrate scopes in good to excellent yields. This hydroxylation provides a green and economic method to synthetize a variety of substituted hydroxylated aromatics (phenols).
나노 사이즈의 불균일 촉매는 표면의 낮은 산화수를 가지는 단점이 있지만, 균일 촉매는 높은 산화수를 가지어 넓은 범위의 반응에 적용 가능성이 있다. 우리는 낮은 산화수(0)의 팔라듐을 높은 산화수(IV)의 팔라듐 물질로 효과적으로 생성하는 연구를 통하여, 선택성 있는 탄소-수소 할로지네이션 반응을 보고한다. 또한 나노 사이즈의 팔라듐의 낮은 산화 상태(0)를 조절하여 높은 산화 상태(IV) 또는 낮은 상화상태(0)를 이용하여 탄소-수소 할로지네이션 반응을 진행한뒤, 탄소-질소, 탄소-탄소, 탄소-황 등의 교차 커플링 반응을 연속적으로 한 반응기 내에서 진행 되는 방법을 성공적으로 개발 하였다.
로듐(III) 촉매를 이용하는 선택성 있는 탄소-수소 브롬화 반응과 요오드화 반응을 2-아릴 아이소퀴놀린 / 피리딘에 효과적으로 진행하여 선택성을 가지는 두개의 아릴 화합물을 합성하는 방법을 개발 하였다.
