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DOI: 10.1055/a-2107-4416
Developing Organometallic Nucleophilic Reagents Via Photoredox Catalysis
P.G.C. acknowledges the Ministero dell’Istruzione, dell’Università e della Ricerca project (PRIN 2017 ID: 20174SYJAF) SURSUMCAT ‘Raising up Catalysis for Innovative Developments’ for financial support of this research and A.G. and P.C. acknowledge the University of Bologna. P.G.C. and A.G. thanks the European Union’s Horizon 2020 research and innovation program under grant agreement No. 951996 (BioMass4Synthons).
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Abstract
The addition of organometallic reagents to the carbonyl group represents a key transformation, both in academia and industry. Most of these transformations rely on a mechanism in which accessible and reactive halides are transformed into the corresponding nucleophilic organometallic reactive compounds through a redox mechanism, using a metal (Cr, Mg, In, etc.) in low oxidation state, by electron transfer. With the advent of photoredox catalysis, the formation of radicals, through oxidation or reduction of suitable and tailored organic precursors, was merged with transition metal catalysis. By radical-to-polar crossover (RPCO), a radical metal is combined with an organic radical to produce, via radical-radical trapping, a polar nucleophilic organometallic reagent. Using dual photoredox catalysis (metallaphotoredox catalysis), a reactive organometallic reagent can be prepared, avoiding the use of metals in low oxidation state. Herein, in addition to the description of the results obtained by our group and the contributions of others on the connection between carbonyl addition and radical-based photochemistry, we provide core guidance for further synthetic developments. We anticipate that extending the photoredox dual strategy beyond the Barbier reactions described here, taming less-activated carbonyls, studying other important electrophiles, will soon realize important breakthroughs.
1 Introduction
2 Photoredox Catalysis: A Survival Guide for the ‘Photo-Curious’
3 Chromium Nucleophilic Organometallic Reagents
3.1 Allylation of Aldehydes
3.2 Allylation of Aldehydes via Dienes
3.3 Propargylation of Aldehydes via 1,3-Enynes
3.4 Alkenylation of Aldehydes
3.5 Alkylation of Aldehydes
3.6 Enantioselective Chromium-Mediated Photoredox Reactions
4 Titanium Nucleophilic Organometallic Reagents
4.1 Allylation Reactions
4.2 Propargylation Reactions
4.3 Allylation Reactions via Dienes
4.4 Benzylation Reactions
4.5 Alkylation Reactions
5. Cobalt Nucleophilic Organometallic Reagents
5.1 Allylation Reactions
6 Conclusion
Key words
photoredox catalysis - dual catalysis - radical-to-polar crossover - carbonyl electrophiles - photoredox Nozaki–Hiyama–Kishi - Ti(III) reactionsPublication History
Received: 05 May 2023
Accepted after revision: 07 June 2023
Accepted Manuscript online:
07 June 2023
Article published online:
17 July 2023
© 2023. Thieme. All rights reserved
Georg Thieme Verlag KG
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For a review of TADF dyes in photoredox catalysis, see: