A radical-polar crossover approach to complex nitrogen heterocycles via the triplet state

19 May 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


The transition from radical to ionic reactivity is a key design feature of many photochemical reactions, enabling complex transformations not possible under either mechanistic regime alone. Ground state alkenes are common substrates in existing methods of this type, serving as radical acceptors to generate open-shell intermediates from which the radical–polar crossover (RPC) event is oxidatively or reductively triggered by a photocatalyst. Here, we describe an alternative RPC mechanism proceeding via an alkene triplet diradical. In this transformation, an iodine radical liberated during a homolytic aromatic substitution step functions as a single electron oxidant to generate an iminium electrophile that can be intercepted en route to complex natural product-like amines. An enantioselective variant of the reaction, enabled by an oxidatively installed sulfinyl leaving group, points to the generality of this underdeveloped pattern of diradical reactivity, paving the way to other triplet-state reactions that incorporate both one and two electron bond-forming processes.


triplet state
energy transfer
radical polar crossover

Supplementary materials

supporting information
This file contain all the data (experimental procedures, characterization data and cartesian coordinates for all DFT calculations) supporting the findings of this study.


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