Visible-Light-Driven α-C(sp3)–H Bond Functionalization of Glycine Derivatives
and Zhen Zhao 1Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
The review "Visible-light-driven α-C(sp3)-H bond functionalization of glycine derivatives" covers very intensively developing area in CH-functionalization synthetic methodology. Glycine derivatives are indeed important compounds for applied and fundamental medicinal chemistry. The review is generally well-written and illustrated. I believe it is suitable for publication in Catalysts after some revisions listed below.
1. In general, reviewer recommends to pay more attention to the experimental results supporting the proposed mechanisms. For example, radical trapping experiments, control experiments with pyruvic acid imine derivatives and nucleophilic reagents.
2. "(2) Stoichiometric radical initiator" – in most cases cited, Stoichiometric reagents used as radical precursors are not "radical initiators". Radical initiator term is only applicable to compounds which produce radicals and initiate radical chain reactions.
3. "Compared to these four strategies, visible-light-driven α-C(sp3)-H bond functionalization continually advances in mild reaction conditions, ration use of solar energy, good reaction efficiency, and consequentially green features [33-37]." – the sentence should be rephrased, because "visible-light-driven α-C(sp3)-H bond functionalization" is actually one of these four strategies.
4. I recommend to improve Scheme 1 or omit it. Now it shows no difference between 3 catalytic system types, moreover, the all of them share the same starting material and product. It looks like there is no difference in application scope either.
5. In the sentence "In the past few decades, the alkyl NHPI ester, a well-known alkyl radical source, was widely employed in visible-light-driven alkylation reactions [57, 58]." – references to updated reviews from other research groups should be added: https://doi.org/10.1002/ejoc.202000525, https://doi.org/10.6023/cjoc202105041. It should also be noted that NHPI ethers have also found numerous similar applications recently https://doi.org/10.1002/ajoc.202200262.
In addition, some new photochemical reactions 10.1021/acs.joc.2c01977, 10.1002/adsc.202200304, 10.1016/j.jcat.2022.09.027, 10.1039/D3CC04580C, 10.1021/acs.joc.2c00149 and closely relevant reviews: https://doi.org/10.1002/pep2.24049, 10.3390/molecules25225270 should be considered for appropriate citation.
Author Response
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Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe review entitled "Visible-light-driven α-C(sp3)-H bond functionalization of glycine derivatives" summarizes the recent advances in the development of visible-light based methods to synthesize glycine derivatives. The topic is quite interesting, the overall scheme adopted in this manuscript is clear and a satisfactory number of references to the literature is present.
What is lacking, from my perspective, is an emphasis on the importance of the light-based methods, their advantages and their drawbacks, and, in the conclusions, a brief discussion on the possible issues related to the attemps to make these processes scalable for industrial purposes. Also, in some examples, it should be very interesting to compare the classical methods to obtain glycine derivatives and the visiible light-based ones. Some points have been mentioned in the work (atom economy, selectivity, sustainability) but they should be better highlighted by the comparison with established methods present in literature or commonly employed in labs.
In the introduction greater emphasis to the green opportunities offered by Visible-light-driven catalysis should be added (Nature Chemistry volume 2, pages 527–532 (2010))
Insert two letters to identify the two motifs in the Scheme 1
Scheme 10 must be in bold.
In the Scheme 14 and in the Scheme 15, different molecules have been indicated with the same number. Correct it.
[Ru(bpy)3]2+ instead of Ru(bpy)32+ in the Scheme 2.
Add identifiers to the molecules in Figure 4.
Line 43:” Compared to these four strategies, visible-light-driven α-C(sp3 )-H bond functionalization” can be replaced with “this latter”.
Line 44: “ration” can be replaced with “rational”.
Lines 56-57: It is widely recognized that the short conjugated system of many glycine derivatives hinders direct absorption of visible light.
Line 81: has been instead of “is”
Line 487: Di Carmine’s group
Line 577: There is a blank page, delete it.
Hint: in some cases, it should be also interesting to compare classical methods to derivatize glycine-based compounds with visible-light-driven methods. In the manuscript it’s not clear why one should choose this kind of catalysis instead of others more traditional.
In the conclusions, amongst the challenges, issues related to the scalability of the process on industrial scale should be mentioned
Author Response
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Reviewer 3 Report
Comments and Suggestions for AuthorsThe review by Yao Tian et al., entitled “Visible-light-driven α-C(sp3)-H bond functionalization of glycine derivatives” will be of interest not only to specialists in the field of catalysis and peptide chemistry, but also to a wide range of chemists. The review covers and systematizes a significant layer of articles on this topic, and can undoubtedly be published after minor corrections:
1. After the first mention of the α-C(sp3)-H bond, in the future you can simply leave the C-H bond, since the modification of other bonds in glycine is not considered in the review.
2. In all schemes it is necessary to either remove the mention of the power of the light source and the reaction time, or indicate these parameters in all schemes
3. Make a single image of compounds 1 COOR or COR. This applies to all diagrams; I consider the best image of the structure of compounds 1 to be the image in scheme 30.
4. It is necessary to carefully double-check the articles cited by the review authors. For example, in schemes 4, 5 COR refers not only to glycine derivatives (esters, amides, peptides) but also to ketones and a tetrahydroisoquinoline derivative. Therefore, in scheme 4 there are 2 examples left, and in scheme 5 there are 30 examples. In scheme 7, nitriles and even dimethylaniline are added to ketones.
5. To scheme No. 7 it is necessary to add a description that free glycine and alanine also react, but the reaction products are decarboxylated.
Author Response
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Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsNothing to say, comments have been fully addressed by the authors. Now, the manuscript can be accepted on this journal.
