Protodesilylation of Arylsilanes by Visible-Light Photocatalysis.

The first visible-light-mediated photocatalytic, metal- and base-free protodesilylation of arylsilanes is presented. The C(sp2)-Si bond cleavage process is catalyzed by a 5 mol % loading of a commercially available acridinium salt upon blue-light irradiation. Two simple approaches have been identified employing either aerobic or hydrogen atom transfer cocatalytic conditions, which enable the efficient and selective desilylation of a broad variety of simple and complex arylsilanes under mild conditions.

Visible light-mediated organophotocatalyzed C-H bond functionalization reactions.

Over the last decade, a variety of methodologies for the direct functionalization of C-H bonds have been developed. Among others, visible light photoredox reactions have recently emerged as one of the most efficient and highly selective processes for the direct introduction of a functionality into organic molecules. Easy reaction setups, as well as mild reaction conditions, make this approach superior to other methodologies applying transition metals or strong oxidants, in terms of both costs and substrate and functional group tolerance. In this review, the recent developments in organophotocatalyzed C-H bond functionalization reactions are presented.

8-Mercaptoquinoline as a Ligand for Enhancing the Photocatalytic Activity of Pt(II) Coordination Complexes: Reactions and Mechanistic Insights.

A family of quinoline-platinum(II) complexes as efficient photocatalysts is presented. Their key characteristic is their easy preparation by coordination of the readily available 8-hydroxy- or 8-thio-quinoline ligands, which are well known for their strong chelating ability to different metal ions. In the different photochemical transformations investigated, such as cross-dehydrogenative coupling, oxidation of arylboronic acids, and asymmetric alkylation of aldehydes, 8-mercaptoquinoline-Pt(II) complex proved to be the most general catalyst. Moreover, quenching experiments showed that, contrary to related methods reported in the literature, these complexes followed an oxidative quenching mechanism in all transformations studied. Besides, simulations performed with high-level ab initio methods of the complexes have helped to understand their photocatalytic activity.

Metal-free desilylative C-C bond formation by visible-light photoredox catalysis.

A newly developed methodology for the use of organosilanes as radical precursors under metal-free and visible-light conditions is presented. The strong oxidant character of the 9-mesityl-10-methylacridinium salt in its excited state enables the transformation of simple silanes to the corresponding carbon-centered radicals, which were trapped by various acceptor molecules.

Novel Oxidative Ugi Reaction for the Synthesis of Highly Active, Visible-Light, Imide-Acridinium Organophotocatalysts.

A newly designed class of acridinium-based organophotocatalysts bearing an imide group at the C9-position is presented. To achieve these unprecedented structures, a synthetic strategy based on a novel straightforward oxidative Ugi-type reaction at the benzylic position of C9-unsubstituted acridanes was developed. The introduction of the imide-unit affords a notable photocatalytic activity enhancement, allowing efficient transformations in different oxidative and reductive visible-light catalytic reactions.