有機合成化学協会誌 2017, 75(2), 98-110.
The acid-base combination chemistry is one of the most reliable concepts for designing high performance catalysts. Acid-base combined catalysts can be classified into two types, ion pair catalysts (type A) and acid-base cooperative catalysts (type B). Type A can be subclassified into acidic/basic/neutral salt catalysts (types A1/A2/A3). Type B can be subclassified into conjugationally noninteractive/interactive acid-base catalysts (types B1/B2). Tailor-made multi-selective catalysts can also be designed based on the acid-base combination chemistry. Our recent progress has been described here.
4,5-Dimethyl-2-Iodoxybenzenesulfonic Acid Catalyzed Site-Selective Oxidation of 2-Substituted Phenols to 1,2-Quinols
Muhammet Uyanik, Tatsuya Mutsuga and Kazuaki Ishihara*
Angew. Chem. Int. Ed. 2017, 56(14), 3956–3960.
Version of Record online: 21 FEB 2017 | DOI: 10.1002/anie.201612463
A site-selective hydroxylative dearomatization of 2-substituted phenols to either 1,2-benzoquinols or their cyclodimers, catalyzed by 4,5-dimethyl-2-iodoxybenzenesulfonic acid with Oxone, has been developed. Natural products such as biscarvacrol and lacinilene C methyl ether could be synthesized efficiently under mild reaction conditions. Furthermore, both the reaction rate and site selectivity could be further improved by the introduction of a trialkylsilylmethyl substituent at the 2-position of phenols. The corresponding 1,2-quinols could be transformed into various useful structural motifs by [4+2] cycloaddition cascade reactions.
▼Ammonium Hypoiodite-Catalyzed Peroxidative
Dearomatization of Phenols
Muhammet Uyanik, Kohei Nishioka, and Kazuaki Ishihara*
Heterocycles, 2017, 95(2), 1132–1147 (Masakatsu Shibasaki's Special Issue).
Published online: 31st January, 2017
Here, we report the first transition metal-free peroxidative dearomatization of phenols using hypoiodite catalysis with TBHP. Hypoiodite salts are generated in situ from the corresponding quaternary ammonium iodides in the presence of TBHP, and the oxidative coupling reaction proceeds efficiently under mild conditions. The dearomatized products are versatile synthetic intermediates for further synthetic transformations to various complex structures including heterocycles. As a demonstration, the further oxidation of the unsaturated peroxide with TBHP afforded the corresponding peroxy epoxide in good yield.