Photochemical Reduction of Quinolines with γ-Terpinene.

The saturation of aromatic scaffolds is valuable for the synthesis of complex rings. Herein, we demonstrate a process for photochemical dearomative reduction of quinolines. The process involves capture of a quinoline excited state with γ-terpinene. Importantly, the reaction is chemoselective as other easily reduced functionalities such as halogens or alkenes do not undergo reduction. The mechanism of the reaction has also been investigated. Finally, the generality of the approach towards other substrates is demonstrated.

Photochemical Dearomative Cycloadditions of Quinolines and Alkenes: Scope and Mechanism Studies.

Photochemical dearomative cycloaddition has emerged as a useful strategy to rapidly generate molecular complexity. Within this context, stereo- and regiocontrolled intermolecular para-cycloadditions are rare. Herein, a method to achieve photochemical cycloaddition of quinolines and alkenes is shown. Emphasis is placed on generating sterically congested products and reaction of highly substituted alkenes and allenes. In addition, the mechanistic details of the process are studied, which revealed a reversible radical addition and a selectivity-determining radical recombination. The regio- and stereochemical outcome of the reaction is also rationalized.

Rh(III)-Catalyzed Denitrogenative [4+2] Annulation of Benzamides and 3-Diazoindolin-2-imines: Expedient Access to Indolo[2,3-c] isoquinolin-5-ones.

An effective and pragmatic strategy for the synthesis of structurally diverse indolo[2,3-c]isoquinolin-5-ones has been developed via a Rh(III)-catalyzed C-H activation and [4+2] annulation reaction of N-methoxybenzamides and 3-diazoindolin-2-imines. The reaction involves the efficient formation of two new (one C-C and one C-N) bonds under operationally simple conditions and has the benefits of a broad substrate scope.