Oxidative Radical NHC Catalysis: Divergent Difunctionalization of Olefins through Intermolecular Hydrogen Atom Transfer.

Oxidative N-heterocyclic carbene (NHC) organocatalysis, typically leading to the formation of acyl azolium reactive intermediates, constitutes one of the most important activation strategies for the NHC-catalyzed chemical transformations. Here, we report an unprecedented oxidative radical NHC catalysis by using peroxyester as the external single-electron oxidant to realize divergent difunctionalization of olefins. The key to success of this chemistry is the catalytic generation of oxygen radicals that could trigger an intermolecular hydrogen atom transfer to activate the inert C-H bonds, thereby enabling the productive radical relay process. With this protocol, commonly used general chemicals could serve as radical precursors to allow efficient synthesis of value-added products in a straightforward and cost-effective manner. Preliminary mechanistic investigations, including control experiments and DFT calculations, shed light on the NHC organocatalytic radical reaction mechanism.

Radical Acylalkylation of 1,3-Enynes To Access Allenic Ketones via N-Heterocyclic Carbene Organocatalysis.

An N-heterocyclic carbene organocatalytic 1,4-difunctionalization of 1,3-enynes was developed. This organocatalytic strategy was suitable for a broad spectrum of substrates to efficiently synthesize allenic ketones bearing diverse substituents. Preliminary mechanistic studies suggest a radical reaction pathway for this organocatalytic acylalkylation process.

Altering intercomponent interactions in a photochromic multi-state [2]rotaxane.

Rotaxanes have attracted much attention because of their challenging constructions and potential applications. In this paper, a multi-state [2]rotaxane, in which a dithienylethene-functionalized dibenzo-24-crown-8 macrocycle was interlocked onto a thread component bearing a 4-morpholin-naphthalimide fluorescent stopper and two distinct recognition sites, namely, dibenzylammonium and N-methyltriazolium recognition sites, was prepared and studied. By introducing a dithienylethene photochrome into the macrocycle component, multi-mode alteration of the intercomponent interactions, such as energy transfer, electron transfer, and charge transfer interaction between the photochrome and the fluorescent naphthalimide stopper could be altered in this multi-state rotaxane system in response to the combination of chemical and photochemical stimuli.