32211-88-4Relevant articles and documents
Development of modifiable bidentate amino oxazoline directing group for Pd-catalyzed arylation of secondary C-H bonds
Chen, Kang,Li, Zhao-Wei,Shen, Peng-Xiang,Zhao, Hong-Wei,Shi, Zhang-Jie
, p. 7389 - 7393 (2015)
Abstract A novel bidentate α-amino oxazolinyl directing group has been developed. Different from previous directing groups, this newly designed directing group was easily prepared from amino acids and modified in structure. This auxiliary preferentially effects functionalization at secondary C(sp3)-H bonds, rather than at aryl C(sp2)-H bonds. The diastereoselectivity of direct arylation between geminal secondary C(sp3)-H bonds in linear molecules has also been realized for the first time with a chiral directing group by remote chirality relay. Two diastereoisomers are produced with the same chiral source by changing the substituents of substrates and aryl halides. A new direction: A multifunctional amino oxazoline directing group that is readily available from amino acids, has been developed, which can induce chemo-, regio- and diastereoselectivity in secondary C(sp3)-H arylation reactions. Furthermore, this directing group is removable and modifiable. Steric control and counterions play important roles in the relayed chirality transfer.
Enantioselective Hydroxylation of Benzylic C(sp3)-H Bonds by an Artificial Iron Hydroxylase Based on the Biotin-Streptavidin Technology
Barnet, Maxime,Peterson, Ryan L.,Rebelein, Johannes G.,Rumo, Corentin,Serrano-Plana, Joan,Ward, Thomas R.
, p. 10617 - 10623 (2020/07/04)
The selective hydroxylation of C-H bonds is of great interest to the synthetic community. Both homogeneous catalysts and enzymes offer complementary means to tackle this challenge. Herein, we show that biotinylated Fe(TAML)-complexes (TAML = Tetra Amido Macrocyclic Ligand) can be used as cofactors for incorporation into streptavidin to assemble artificial hydroxylases. Chemo-genetic optimization of both cofactor and streptavidin allowed optimizing the performance of the hydroxylase. Using H2O2 as oxidant, up to ～300 turnovers for the oxidation of benzylic C-H bonds were obtained. Upgrading the ee was achieved by kinetic resolution of the resulting benzylic alcohol to afford up to >98% ee for (R)-tetralol. X-ray analysis of artificial hydroxylases highlights critical details of the second coordination sphere around the Fe(TAML) cofactor.
Unifying Evaluation of the Technical Performances of Iron-Tetra-amido Macrocyclic Ligand Oxidation Catalysts
Denardo, Matthew A.,Mills, Matthew R.,Ryabov, Alexander D.,Collins, Terrence J.
, p. 2933 - 2936 (2016/03/19)
The main features of iron-tetra-amido macrocyclic ligand complex (a sub-branch of TAML) catalysis of peroxide oxidations are rationalized by a two-step mechanism: FeIII + H2O2 → Active catalyst (Ac) (kI), and Ac + Substrate (S) → FeIII + Product (kII). TAML activators also undergo inactivation under catalytic conditions: Ac → Inactive catalyst (ki). The recently developed relationship, ln(S0/S∞) = (kII/ki)[FeIII]tot, where S0 and S∞ are [S] at time t = 0 and ∞, respectively, gives access to ki under any conditions. Analysis of the rate constants kI, kII, and ki at the environmentally significant pH of 7 for a broad series of TAML activators has revealed a 6 orders of magnitude reactivity differential in both kII and ki and 3 orders differential in kI. Linear free energy relationships linking kII with ki and kI reveal that the reactivity toward substrates is related to the instability of the active TAML intermediates and suggest that the reactivity in all three processes derives from a common electronic origin. The reactivities of TAML activators and the horseradish peroxidase enzyme are critically compared.
