4,5‐Dimethyl‐2‐Iodoxybenzenesulfonic Acid Catalyzed Site‐Selective Oxidation of 2‐Substituted Phenols to 1,2‐Quinols

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.     

Hypervalent Iodine(III)‐Mediated Oxidative Fluorination of Alkylsilanes by Fluoride Ions

The first example of a hypervalent iodine(III)‐mediated oxidative fluorination of alkylsilanes by fluoride ions without the use of transition metals is demonstrated. This reaction is operationally simple, scalable, and proceeds under mild reaction conditions. Mechanistic studies suggest the involvement of a single‐electron transfer resulting from the interaction of an organopentafluorosilicate and aryliodonium difluoride, which were generated in situ from the corresponding alkylsilane and iodosobenzene, respectively, in the presence of fluoride ions.     

Dearomatization of Electron‐Deficient Phenols to ortho‐Quinones: Bidentate Nitrogen‐Ligated Iodine(V) Reagents

Despite their broad utility, the synthesis of ortho‐quinones remains a significant challenge, in particular, access to electron‐deficient derivatives remains an unsolved problem. Reported here is the first general method for the synthesis of electron‐deficient ortho‐quinones by direct oxidation of phenols. The reaction is enabled by a novel bidentate nitrogen‐ligated iodine(V) reagent, a previously unexplored class of compounds which we have termed Bi(N)‐HVIs. The reaction is extremely general and proceeds with excellent regioselectivity for the ortho over para isomer. Functionalization of the ortho‐quinone products was examined, resulting in a facile one‐pot synthesis of catechols, as well as the incorporation of a variety of heteroatom nucleophiles. This method represents the first synthetic application of Bi(N)‐HVIs and demonstrates their potential as a platform for the further development of highly reactive, but also highly tunable, I(V) reagents.