A ligand-free and operationally simple copper-catalyzed aerobic benzylic sp3 C–H oxygenation was developed. The addition of tert-butyl hydroperoxide, either in a catalytic or stoichiometric amount, was key for activating stable C–H bonds under mild conditions to furnish the corresponding ketones or esters in moderate to excellent yield.
Enantioselective Copper-Catalyzed Alkynylation of Benzopyranyl Oxocarbenium Ions
作者:Harathi D. Srinivas、Prantik Maity、Glenn P. A. Yap、Mary P. Watson
DOI:10.1021/acs.joc.5b00364
日期:2015.4.17
We have developed highly enantioselective, copper-catalyzedalkynylations of benzopyranyl acetals. By using a copper(I) catalyst equipped with a chiral bis(oxazoline) ligand, high yields and enantioselectivities are achieved in the alkynylation of widely available, racemic isochroman and chromene acetals to deliver α-chiral oxygen heterocycles. This method demonstrates that chiral organometallic nucleophiles
Organocatalytic Aerobic Oxidation of Benzylic sp<sup>3</sup> C–H Bonds of Ethers and Alkylarenes Promoted by a Recyclable TEMPO Catalyst
作者:Zhiguang Zhang、Yuan Gao、Yuan Liu、Jianjun Li、Hexin Xie、Hao Li、Wei Wang
DOI:10.1021/acs.orglett.5b02877
日期:2015.11.6
An entirely metal-free catalyst system consisting of an easily prepared recyclable new TEMPO derived sulfonic salt catalyst, and mineral acids (NaNO2 and HCl) has been developed for selective aerobic oxidation of structurally diverse benzylic sp(3) C-H bonds of ethers and alkylarenes. The mild reaction conditions allow for the generation of synthetically and biologically valued isochromanones and xanthones from readily accessible alkyl aromatic precursors in good yields.
Photocycloaddition of Isocoumarins and Isothiocoumarins to Alkenes
On irradiation in the presence of tetrachloroethene (TCE), both isocoumarins 3 and isothiocoumarins 4 afford in high yields the cis-fused cycloadducts 8 and 9, while only the oxacycles 3 undergo photocycloaddition to 2,3-dimethylbut-2-ene (TME) to give mixtures of cis- and trans-fused products 10 and 11, respectively, in moderate yields. This higher efficiency in reacting with TCE as compared to TME for compounds 3 and 4 contrasts the behavior of simple cyclic enones, e.g., 5,5-dimethylcyclohex-2-enone (12), which is converted to bicyclooctanones about fifty times faster with TME than with TCE.