The 21 Must-Read Photochemistry Papers of 2021

A belated year in review 2021

Before we get to the 21 best photochemistry papers of 2021, we want to look back at the year.  And at HepatoChem, we had a VERY big year in 2021. We started shipping our new photoreactor the Lucent360™, added members to our team, moved into a new lab space and built out a new manufacturing facility. The year 2022 promises even more, new products, more exciting photochemistry, and hopefully more fun posts in our blog.

Last year at this time, while looking ahead towards a long cold COVID filled winter, we decided to look back at the year 2020 with a fun little piece listing our favorite papers of the year. Now, everything has changed. COVID has gone away, the world has returned to normal, and everyone’s reagents and supplies are showing up on time. Little did we all know then that 2020 would never end. So, as we head into the 25th month of 2020, we try again to look back at the past 12 months of visible-light photocatalysis, photoredox, and synthetic photochemistry (really, we all need to just agree on a single term). Everything else arrived late in the past year, why not this?

Last year, we estimated that there were a few thousand visible light photochemistry papers published in 2020, which seemed like a lot. Now as we look back at 2021, there is likely several times more. We’ve even reached the point where we are seeing papers titled “Light-free catalysis…” (not to call anyone out, but this used to be called catalysis). It continues to amaze us the amount of great work being published out there, especially with all the hardships and difficulties day to day endured just simply to get to work in the lab. As we described last year, these are our favorite 21 photocatalysis papers from 2021. This is not a list that attempts to find the best, or most viewed, or most famous 21 papers from the year. (We don’t have the time, energy, or interest in something that exhaustive and complex). Last year, we described our general criteria here. Instead, this list of the 21 must-read photochemistry papers of 2021 are simply ones that we thought were the best, funniest, oddest, most interesting, or downright unexpected. There are no bonus points for using any of our products, but I can’t say it wouldn’t help either.

As a few added rules, this year, we eliminated from contention any paper using the terms variant, strain, antibody, viral, or anti-viral. So, we apologize. Even if your paper “A new photocatalytic variant of the Minisci reaction for labeling coronavirus antibodies” is the greatest piece of literature ever prepared, we won’t be reading it or highlighting it to avoid triggering our audience in this hellscape that we live. To answer a comment from our list from last year, our focus is definitely biased towards synthetic photoredox. So, all the great papers out there in more traditional photochemistry, solar cell, energy research and materials are generally not on our radar and likely not included on this list. If you have made that list, send it our way, we would love to read it. So, let’s have some fun. Keeping reading for our favorite papers from 2021 and then send us your favorites on twitter (@EvoluChem) or at info@hepatochem.


Paper 1:

C(sp3)–H methylation enabled by peroxide photosensitization and Ni-mediated radical coupling

Authors: Aristidis Vasilopoulos, Shane W. Krska, Shannon S. Stahl
Ref: Science 372, 398–403 (2021)

Comment: To start us off, a very cool, simple C-C bond formation reaction on a diverse set of pharmacologically relevant substrates.


Paper 2:

Switchable, Reagent-Controlled Diastereodivergent Photocatalytic Carbocyclisation of Imine-Derived α-Amino Radicals.

(open access)
J. Andrew P. Maitland, Jamie A. Leitch, Ken Yamazaki, Kirsten E. Christensen, Doyle J. Cassar, Trevor A. Hamlin, and Darren J. Dixon
Ref: Angew. Chem. Int. Ed. 2021 60 (45), 24116-24123

Comment: The selectivity and switchability observed on this complex cyclization based on temperature, wavelength, and condition is fascinating and we’re still digging into many of the details on this one.


Paper 3:

Copper-Mediated Radical-Polar Crossover Enables Photocatalytic Oxidative Functionalization of Sterically Bulky Alkenes

Authors: Nicholas L. Reed, Grace A. Lutovsky, and Tehshik P. Yoon
Ref: J. Am. Chem. Soc. 2021, 143 (16), 6065–6070

Comment: A nice example of the power of photochemistry where you can replace expensive palladium catalysts with inexpensive copper salts and light, while also extending the value of the reaction.


Paper 4:

A biomimetic SH2 cross-coupling mechanism for quaternary sp3-carbon formation

(open access)
Wei Liu, Marissa N. Lavagnino, Colin A. Gould, Jesús Alcázar, David W. C. MacMillan
Ref: Science 374, 1258–1263 (2021)

Comment: A Nobel prize winner also dabbles a bit in photochemistry. Like every year we could also have picked any number of papers like this one on copper photochemistry or tyrosine bioconjugation. But this one uses an iron porphyrin and we’re a little bit biased towards those around here


Paper 5:

Photochemical intermolecular dearomative cycloaddition of bicyclic azaarenes with alkenes

Authors: Jiajia Ma, Shuming Chen, Peter Bellotti, Renyu Guo, Felix Schäfer, Arne Heusler, Xiaolong Zhang, Constantin Daniliuc, M. Kevin Brown, Kendall N. Houk, Frank Glorius
Ref: Science 371, 1338–1345 (2021)

Comment: A really cool example of a photochemical intermolecular cycloaddition to quickly generate a diverse set of compounds.


Paper 6:

The Open Reaction Database

Authors: Steven M. Kearnes, Michael R. Maser, Michael Wleklinski, Anton Kast, Abigail G. Doyle, Spencer D. Dreher, Joel M. Hawkins, Klavs F. Jensen, and Connor W. Coley
Ref: J. Am. Chem. Soc. 2021, 143 (45), 18820–18826

Comment: While not primarily photocatalysis focused, this is a very cool project for sharing and archiving chemical data that we hope takes off.


Paper 7:

Illuminating Life’s Origins: UV Photochemistry in Abiotic Synthesis of Biomolecules

(open access)
Authors: Nicholas J. Green, Jianfeng Xu, and John D. Sutherland
Ref: J. Am. Chem. Soc. 2021, 143, 19, 7219–7236

Comment: An in depth look at some of the reactions that are possible with solar radiation and primordial soup.


Paper 8:

Unveiling Potent Photooxidation Behavior of Catalytic Photoreductants

Authors: Karina Targos, Oliver P. Williams, and Zachary K. Wickens
Ref: J. Am. Chem. Soc. 2021, 4125–4132

Comment: We could have chosen from any number of great papers from the Wicken’s group this year to highlight. We wrote about this one in depth back in April.


Paper 9:

Site-Selective Installation of NƐ-Modified Side Chains into Peptides and Proteins via Visible-Light-Mediated Desulfurative C-C Bond Formation

(open access)
Authors: Rhys C. Griffiths, Frances R. Smith, Jed E. Long, Daniel Scott, Huw E. L. Williams, Neil J. Oldham, Robert Layfield, and Nicholas J. Mitchell
Ref: Angew. Chem 2021, ASAP

Comment: Want to know a great way to get our attention? Report a reaction that takes an hour in a standard setup and 2 minutes in a PhotoRedox Box.


Paper 10:

Flowers of the Plant Genus Hypericum as Versatile Photoredox Catalysts

Authors: Jun-jie Wang, Kai Schwedtmann, Kun Liu, Stephen Schulz, Jan Haberstroh, Gerrit Schaper, Anja Wenke, Julia Naumann, Torsten Wenke, Stefan Wanke and Jan J. Weigand
Ref: Green Chem. 2021, 23 (2), 881–888

Comment: Perhaps the most fun and unexpected paper we read in 2021. Flowers as photocatalysts. We wrote about this one in depth back in March.


Paper 11:

A Maze in Plastic Wastes: Autonomous Motile Photocatalytic Microrobots against Microplastics

Authors: Seyyed Mohsen Beladi-Mousavi, Soňa Hermanová, Yulong Ying, Jan Plutnar, and Martin Pumera
Ref: ACS Appl. Mater. Interfaces 2021, 13 (21), 25102–25110

Comment: A fun paper with robots, mazes, plastics and photochemistry that we wrote about in depth in May.


Paper 12:

Mechanistic Investigations of an α-Aminoarylation Photoredox Reaction

Authors: Bernard G. Stevenson, Ethan H. Spielvogel, Emily A. Loiaconi, Victor Mulwa Wambua, Roman V. Nakhamiyayev, and John R. Swierk
Ref: JACS 2021 143 (23), 8878-8885

Comment: The first paper from the Swierk group. Second paper interesting as well. Please keep looking deeply into the oddities of photoredox.


Paper 13:

Practical and Selective sp3 C-H Bond Chlorination via Aminium Radicals

(open access)
Authors: Alastair J. McMillan, Martyna Sienkowska, Piero Di Lorenzo, Gemma K. Gransbury, Nicholas F. Chilton, Michela Salamone, Alessandro Ruffoni, Massimo Bietti, and Daniele Leonori
Ref: Angew. Chem. Int. Ed. 2021. 60 (13), 7132-7139

Comment: We’ve chlorinated a few things in our time (not always intentionally). Simple and selective methods are always welcome.


Paper 14:

Predicting Wavelength-Dependent Photochemical Reactivity and Selectivity

(open access)
Authors: Jan P. Menzel, Benjamin B. Noble, James P. Blinco and Christopher Barner-Kowollik
Ref: Nature Communications 12, Article number: 1691 (2021)

Comment: Sometimes it easiest to just shine every wavelength of light you own on a problem. Other people try to predict what would happen first. We tend towards the former approach but will always read interesting articles from those who know how to approach the problem in a better way.


Paper 15:

Aza-Heterocycles via Copper-Catalyzed, Remote C–H Desaturation of Amines

Authors: Leah M. Stateman, Ross M. Dare, Alyson N. Paneque, David A. Nagib
Ref: Chem 2021 ASAP

Comment: 2021 might have been the year of copper. Or the year of heterocycles. But it was definitely a year of fun and interesting in-depth mechanistic works like this one.


Paper 16:

Photocatalytic Hydroaminoalkylation of Styrenes with Unprotected Primary Alkylamines

Authors: Hannah E. Askey, James D. Grayson, Joshua D. Tibbetts, Jacob C. Turner-Dore, Jake M. Holmes, Gabriele Kociok-Kohn, Gail L. Wrigley, and Alexander J. Cresswell
Ref: J. Am. Chem. Soc. 2021, 143 (39), 15936–15945

Comment: Hey, those spirocyclic compounds look fun.


Paper 17:

Synthesis of α-Quaternary Bicyclo[1.1.1]Pentanes through Synergistic Organophotoredox and Hydrogen Atom Transfer Catalysis

Authors: Jeremy Nugent, Alistair J. Sterling, Nils Frank, James J. Mousseau, and Edward A. Anderson
Ref: Org. Lett. 2021, 23, 8628-8633

Comment: Nice photoreactor.


Paper 18:

Photochemical C–H Arylation of Heteroarenes for DNA-Encoded Library Synthesis

(open access)
Authors: Matthias Krumb, Lisa Marie Kammer, Shorouk O. Badir, María Jesús Cabrera-Afonso, Victoria E. Wu, Minxue Huang, Adam Csakai, Lisa A. Marcaurelle and Gary A Molander
Ref: Chemical Science, 2021, ASAP

Comment: We’re still amazed every time we see something like this work.


Paper 19:

Radical Decarboxylative Carbometalation of Benzoic Acids: A Solution to Aromatic Decarboxylative Fluorination

Authors: Peng Xu, Priscila López-Rojas, and Tobias Ritter
Ref: J. Am. Chem. Soc. 2021, 143 (14), 5349–5354

Comment: I think we can find a use for this reaction. Just a guess.


Paper 20:

Photochemical Transformation of Chlorobenzenes and White Phosphorus into Arylphosphines and Phosphonium Salts

Authors: Marion Till, Verena Streitferdt, Daniel J. Scott, Ruth M. Gschwind and Robert Wolf
Ref: Chem. Commun, 2021, ASAP

Comment: Sometimes the simplest reactions are the most interesting. This seems like a useful inexpensive way to make phosphines.


Paper 21:

Combining Machine Learning and High-Throughput Experimentation to Discover Photocatalytically Active Organic Molecules

Authors: Xiaobo Li, Phillip M. Maffettone, Yu Che, Tao Liu, Linjiang Chen and Andrew I. Cooper
Ref: Chem. Sci. 2021, 12 (32), 10742–10754

Comment: Recycling a comment from above…Sometimes it easiest to just shine a light on every highly aromatic compound that you have. Other people try to predict what would happen first. We tend towards the former approach but will always read interesting articles from those who know how to approach the problem from the better way.


Paper 22:

A General Strategy for C(sp3)–H Functionalization with Nucleophiles Using Methyl Radical as a Hydrogen Atom Abstractor

Authors: Isabelle Nathalie-Marie Leibler, Makeda A. Tekle-Smith and Abigail G. Doyle
Ref: Nat. Commun. 2021, ASAP

Comment: We started the list with a methylation and we’ll end with a methyl radical abstraction facilitating a set of C-H functionalization reactions.


Reviews Section

Next month’s newsletter could have been our favorite 21 photocatalysis reviews from 2021 because it seems like just about everyone wrote a review in the past year. But we would be remiss if we didn’t share a few of our favorites here that caught our eye from quality and topic.


Review 1:

Technological Innovations in Photochemistry for Organic Synthesis: Flow Chemistry, High-Throughput Experimentation, Scale-up, and Photoelectrochemistry

Authors: Laura Buglioni, Fabian Raymenants, Aidan Slattery, Stefan D. A. Zondag, and Timothy Noël
Ref: Chem. Rev. 2021, ASAP

Comment: A phenomenal review on the photochemistry fundamentals, photoreactors and photoelectrochemistry.


Review 2:

Photons or Electrons? A Critical Comparison of Electrochemistry and Photoredox Catalysis for Organic Synthesis

Authors: Nicholas E. S. Tay, Dan Lehnherr, and Tomislav Rovis
Ref: Chem. Rev. 2021, ASAP

Comment: A great review comparing the fields of photochemistry and electrochemistry and the redox principles that define each process.


Review 3:

Metallaphotoredox: The Merger of Photoredox and Transition Metal Catalysis

Authors: Amy Y. Chan, Ian B. Perry, Noah B. Bissonnette, Benito F. Buksh, Grant A. Edwards, Lucas I. Frye, Olivia L. Garry, Marissa N. Lavagnino, Beryl X. Li, Yufan Liang, Edna Mao, Agustin Millet, James V. Oakley, Nicholas L. Reed, Holt A. Sakai, Ciaran P. Seath, and David W. C. MacMillan
Ref: Chem. Rev. 2021 ASAP

Comment: Photocatalysis review focusing on the recent examples merging visible light photochemistry with organometallic catalytic cycles.


Review 4:

Photocatalysis in the Life Science Industry

Authors: Lisa Candish, Karl D. Collins, Gemma C. Cook, James J. Douglas, Adrián Gómez-Suárez, Anais Jolit, and Sebastian Keess
Ref: Chem. Rev. 2021 ASAP

Comment: Thorough review focusing on photochemical methodologies influence on the pharma and agricultural small molecule and biomolecular applications.


Review 5:

External Fields Enhanced Photocatalysis

Authors: Cheng Hu, Shuchen Tu, Na Tian, Tianyi Ma, Yihe Zhang, and Hongwei Huang
Ref: Angew. Chemie Int. Ed. 2021, 60 (30), 16309-16328

Comment: And finally, a seemingly weird topic that we know very little about. But once you start thinking about it, kind of breaks your mind.


If you made it this far, thanks. Hope everyone out there has a great 2022.


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