We report the application of a chiral triazole-substituted iodoarene in a direct enantioselective hydroxylation of alkyl arenes. This method allows the rapid synthesis of chiral benzyl alcohols in high yields and exceptional stereocontrol despite its non-templated nature. In a unique cascade activation comprising of an initial irradiation-induced radical C-Hbromination and a consecutive enantioconvergent hydroxylation, the iodoarene catalyst has a dual role. It initiates the radical bromination in its oxidized state through an in situ formed bromoiodane and in the second, Cu-catalyzed step, it acts as a chiral ligand. To the best of our knowledge this the first example demonstrating the ability of a chiral aryl iodide catalyst acting both, as an oxidant and as a chiral ligand in a highly enantioselective C-H-activating transformation. Furthermore, this is the first example for an enantioconvergent hydroxylation. zylic C-H-bond in the presence tertiary C-H-bonds was observed. This unique reaction cascade offers great potential for other enantioselective oxidative benzylic C-H-activations, although the mechanism of the enantioconvergent step still needs to be further elaborated.
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The direct hydroxylation of 2-aryloxazolines via a deprotonative magnesiation using TMPMgCl•LiCl and subsequent oxidation with molecular oxygen or air as a green oxidant is reported. This method proceeds under mild conditions at room temperature with high regioselectivity and chemoselectivity. The obtained phenols exhibit tunable luminescence properties, induced by excited-state intramolecular proton transfer. This method opens a new opportunity for the sustainable synthesis of luminescent organic molecules.
A highly regioselective functionalization of 7-bromofluorene-2-carbaldehydes, potent organic chromophores, in position C3 using a mild ortho-metallation strategy (DoM) with TMPMgCl·LiCl has been developed. This approach allows the preparation of highly functionalized fluorene derivatives by conversion of the in situ generated metalated species with various electrophiles giving a fast access to novel organic phosphorescent dyes.
In this article we describe an enantioselective hydroxylation of benzylic C-H bonds with a unique activation mechanism. A chiral aryl iodide catalyst initially acts as precursor for a brominating reagent which subsequently brominates the benzylic C-H bond in a non-stereoselective fashion through a radical bromination. In the second step of this transofrmation, the same catalyst acts as a chiral ligand in a Cu-catalyzed enantioconvergent substitution. We present a broad substrate scope and an intial mechanistic proposal based on a plethora of control experiments.<br>
In this article we describe an enantioselective hydroxylation of benzylic C-H bonds with a unique activation mechanism. A chiral aryl iodide catalyst initially acts as precursor for a brominating reagent which subsequently brominates the benzylic C-H bond in a non-stereoselective fashion through a radical bromination. In the second step of this transofrmation, the same catalyst acts as a chiral ligand in a Cu-catalyzed enantioconvergent substitution. We present a broad substrate scope and an intial mechanistic proposal based on a plethora of control experiments.<br>
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