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This Account summarizes efforts in our group toward synthesis of heterocycles in the past decade. Selected examples of transannulative heterocyclizations, intermediate construction of reactive compounds en route to these important motifs, and newer developments of a radical approach are outlined.

1 Introduction

2 Transannulative Heterocyclization

2.1 Rhodium-Catalyzed Transannulative Heterocyclization

2.2 Copper-Catalyzed Transannulative Heterocyclization

3 Synthesis of Heterocycles from Reactive Precursors

3.1 Synthesis of Heterocycles from Diazo Compounds

3.2 Synthesis of Heterocycles from Alkynones

4 Radical Heterocyclization

4.1 Light-Induced Radical Heterocyclization

4.2 Light-Free Radical Heterocyclization

7 Conclusion

Dual light-excited ketone/transition-metal catalysis is a rapidly developing field of photochemistry. It allows for versatile functionalizations of C–H or C–X bonds enabled by triplet ketone acting as a hydrogen-atom-abstracting agent, a single-electron acceptor, or a photosensitizer. This review summarizes recent developments of synthetically useful transformations promoted by the synergy between triplet ketone and transition-metal catalysis.

1 Introduction

2 Triplet Ketone Catalysis via Hydrogen Atom Transfer

2.1 Triplet Ketones with Nickel Catalysis

2.2 Triplet Ketones with Copper Catalysis

2.3 Triplet Ketones with Other Transition-Metal Catalysis

3 Triplet Ketone Catalysis via Single-Electron Transfer

4 Triplet Ketone Catalysis via Energy Transfer

5 Conclusions

A mild visible light‐induced palladium‐catalyzed alkyl Heck reaction of diazo compounds andN‐tosylhydrazones is reported. A broad range of vinyl arenes and heteroarenes with high functional group tolerance, as well as a range of different diazo compounds, can efficiently undergo this transformation. This method features Brønsted acid‐assisted generation of hybrid palladium C(sp³)‐centered radical intermediate, which allowed for new selective C−H functionalization protocol.

Aliphatic allylic amines are found in a great variety of complex and biorelevant molecules. The direct allylic C–H amination of alkenes serves as the most straightforward method toward these motifs. However, use of widely available internal alkenes with aliphatic amines in this transformation remains a synthetic challenge. In particular, palladium catalysis faces the twin challenges of inefficient coordination of Pd(II) to internal alkenes but excessively tight and therefore inhibitory coordination of Pd(II) by basic aliphatic amines. We report a general solution to these problems. The developed protocol, in contrast to a classical Pd(II/0) scenario, operates through a blue light–induced Pd(0/I/II) manifold with mild aryl bromide oxidant. This open-shell approach also enables enantio- and diastereoselective allylic C–H amination.