General Synthesis of Retinoids and Arotinoids via Palladium-Catalyzed Cross-Coupling of Boronic Acids with Electrophiles
作者:Alicia Torrado、Susana López、Rosana Alvarez、Angel R. de Lera
DOI:10.1055/s-1995-3905
日期:1995.3
A novel approach to the synthesis of retinoids and arotinoids (including heterocyclic analogs) is described which is based on the thallium-accelerated palladium-catalyzed cross-coupling of boronic acids with a variety of electrophiles (the Suzuki reaction).
The synthesis of two new unsymmetric dinucleating ligandsystems, L1, combining a bidentate binding site with a tridentate binding site linked through a dibenzofuran spacer, and L2, with two tridentate binding sites bridged by an ethylene spacer, is reported. The ligands L1 and L2 were used for the preparation of the dicopper(I) complexes [Cu2(L1)(NCCH3)3](X)2, [Cu2(L1)Cl2]}n and [Cu2(L2)(NCCH3)2](Y)2
Proton-Coupled O−O Activation on a Redox Platform Bearing a Hydrogen-Bonding Scaffold
作者:Christopher J. Chang、Leng Leng Chng、Daniel G. Nocera
DOI:10.1021/ja028548o
日期:2003.2.19
Porphyrin architectures bearing a hydrogen-bonding scaffold have been synthesized. The H-bond pendant allows proton-coupled electron transfer (PCET) to be utilized as a vehicle for effecting catalytic O-O bond activation chemistry. Suzuki cross-coupling reactions provide a modular synthetic strategy for the attachment of porphyrins to a rigid xanthene or dibenzofuran pillar bearing the H-bond pendant. The resulting HPX (hanging porphyrin xanthene) and HPD (hanging porphyrin dibenzofuran) systems permit both the orientation and acid-base properties of the hanging H-bonding group to be controlled. Comparative reactivity studies for the catalase-like disproportionation of hydrogen peroxide and the epoxidation of olefins by the HPX and HPD platforms with acid and ester hanging groups reveal that the introduction of a proton-transfer network, properly oriented to a redox-active platform, can orchestrate catalytic O-O bond activation. For the catalase and epoxidation reaction types, a marked reactivity enhancement is observed for the xanthene-bridged platform appended with a pendant carboxylic acid group, establishing that this approach can yield superior catalysts to analogues that do not control both proton and electron inventories.
Schwartz, Elaine Benaksas; Knobler, Carolyn B.; Cram, Donald J., Journal of the American Chemical Society, 1992, vol. 114, # 27, p. 10775 - 10784
作者:Schwartz, Elaine Benaksas、Knobler, Carolyn B.、Cram, Donald J.