Light-enabled, AlCl3-catalyzed regioselective intramolecular nucleophilic addition of non-nucleophilic alkyls to alkynes.

Light-enabled, AlCl3-catalyzed regioselective intramolecular nucleophilic cyclization of alkynes using non-nucleophilic alkyls as the nucleophile is reported. Upon photoexcitation, o-alkylphenyl alkynyl ketones can be transferred into (E)-photoenols. Thus, a nucleophilic methylene is formed from the non-nucleophilic alkyl. An AlCl3 catalyst can stabilize the (E)-photoenol intermediate and facilitate further intramolecular nucleophilic cyclization. DFT calculations indicated that the AlCl3-catalyzed cyclization is the regioselectivity determining step.

Cu(II)-Catalyzed 6π-Photocyclization of Non-6π Substrates.

This research successfully achieved a Cu(II)-catalyzed 6π-photocyclization of non-6π substrates. The photoenolization converts ortho-alkylphenyl alkynl ketones into a triene-type intermediate which undergoes the subsequent 6π-photocyclization to give naphthol as the final product. Cu(II) catalyst facilitates both photoenolization and 6π-photocyclization. This research highlighted the tandem reaction strategy and the importance of metal catalysis in photochemistry.

Transformation of Organostannanes Based on Photocleavage of C-Sn Bond via Single Electron Transfer Process.

In this work, we developed a new method for the transformation of organostannanes via radical process. In this reaction, highly reactive carbon radical species can be efficiently generated through HBr-catalyzed photocleavage of C-Sn bond via single electron transfer process. Under aerobic conditions, the in situ formed primary/secondary alkyl radicals can be further highly selectively oxidized into carboxylic acids/ketones, respectively.

Cu(II)-Catalyzed 6π-Photocyclization of Dienynes.

The first 6π-photocyclization of dienynes was developed, which provides a new and effective protocol for the synthesis of the phenyl ring in excellent yields with nice functional group tolerance. In this transformation, the Cu(OTf)2 catalyst plays a key role in the conversion of alkyne moiety into an alkene-type moiety, which means that the dienyne reactant is converted into a triene-type substrate. Thus, this reaction proceeds via a Cu(II)-catalyzed 6π-photocyclization of triene-type derivatives.

Merging photoredox catalysis with Lewis acid catalysis: activation of carbon-carbon triple bonds.

Here, we demonstrate that merging photoredox catalysis with Lewis acid catalysis provides a fundamentally new activation mode of C-C triple bonds, to achieve the bond-forming reaction of alkynes with weak nucleophiles. Using a synergistic merger of Eosin Y and Cu(OTf)2, a highly efficient cyclization reaction of arene-ynes was developed.