Yang Jenny Y, Bachmann Julien, Nocera Daniel G
Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4301, USA.
J Org Chem. 2006 Nov 10;71(23):8706-14. doi: 10.1021/jo0613075.
A synthetic strategy for the construction of chiral salen ligands bearing two rigid xanthene spacers functionalized with carboxylic acid and ester groups is presented. Suzuki cross-coupling methodology is used to furnish the appropriately functionalized xanthene spacers to a salicylaldehyde, which is subsequently condensed with (1R,2R)-(-)-1,2-diaminocyclohexane to produce salen ligands featuring an expandable molecular cleft capable of multiple hydrogen-bonding interactions in addition to metallosalen oxidation chemistry. The ability of these "Hangman" platforms to support multielectron chemistry mediated by proton-coupled electron transfer (PCET) is established by their proclivity to promote the catalytic disproportionation of hydrogen peroxide to oxygen and water via a high-valent metal oxo. Within this functionalized Hangman framework, the stereochemistry of the cyclohexyl backbone of the salen platform is revealed in the epoxidation of 1,2-dihydronaphthalene by the metal oxo.
本文提出了一种合成策略，用于构建带有两个由羧酸和酯基官能化的刚性氧杂蒽间隔基的手性双水杨醛缩乙二胺配体。采用铃木交叉偶联方法将适当官能化的氧杂蒽间隔基连接到水杨醛上，随后将其与(1R,2R)-(-)-1,2-二氨基环己烷缩合，以制备具有可扩展分子裂缝的双水杨醛缩乙二胺配体，该配体除了具有金属双水杨醛氧化化学性质外，还能够进行多种氢键相互作用。这些“刽子手”平台通过高价金属氧代促进过氧化氢催化歧化为氧气和水的倾向，证实了它们支持由质子耦合电子转移(PCET)介导的多电子化学的能力。在这个官能化的“刽子手”框架内，金属氧代在1,2-二氢萘的环氧化反应中揭示了双水杨醛平台环己基主链的立体化学。
