Different Chiral Ligands Assisted Enantioselective C-H Functionalization with Transition-Metal Catalysts
and Hong-Liang Li 2,3,*
Round 1
Reviewer 1 Report
This review article summarizes some recent developments in the enantioselective C-H bond functionalization promoted by transition metal complexes. All major relevant literature items have been discussed in detail, including the achievements of the authors themselves who have extensive and documented experience in the field. In terms of content, the text was correctly written, but requires careful linguistic correction, as it contains a large number of grammatical, stylistic and spelling errors too numerous to list in detail.
Minor points:
Page 6, the sentence that begins with “Amino acids as chiral ligand used in enantioselective C-H functionalization has been investigated due to their merits, such as easy preparation from commercially available and naturally occurring amino acids…” is not clear and needs correction
Page 9, the sentence “The highly sterically phosphine oxide…” is not clear
Page 11, the sentence “Recently, the development of enantioselective version of C-H borylation by Sawamura’s group and Xu’s group is more significant in synthetic chemistry” is not clear.
In many schemes, the use of an apostrophe after the author's name is not necessary
Author Response
- [Comment #1]
Page 6, the sentence that begins with “Amino acids as chiral ligand used in enantioselective C-H functionalization has been investigated due to their merits, such as easy preparation from commercially available and naturally occurring amino acids…” is not clear and needs correction.
[Response]
We have revised the original sentence to “Given their easy preparation form commercially available and naturally occurring amino acids as well as their ability to coordinate with transition-metal, amino acid derivatives have been investigated in the desymmetrization of different types of C-H bonds.”
- [Comment #2]
Page 9, the sentence “The highly sterically phosphine oxide…” is not clear.
[Response]
We have revised the original sentence to “The sterically hindered phosphine oxide…”
- [Comment #3]
Page 11, the sentence “Recently, the development of enantioselective version of C-H borylation by Sawamura’s group and Xu’s group is more significant in synthetic chemistry” is not clear.
[Response]
We have revised the original sentence to “Recently, the development of enantioselective borylation of C-H bonds by Sawamura’s group and Xu’s group is of great significance.”
- [Comment #4]
In many schemes, the use of an apostrophe after the author's name is not necessary.
[Response]
According to the suggestion of reviewer, we have delete all apostrophe.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors contributed a well-organized informative review on the topic of C-H activation with a focus on the enantioselective sp3 C-H functionalization using chiral ligands. The topic is important and the review is well-written, therefore, should be published in Catalysts. Following are minor questions and concerns:
- This review only focuses on sp3 C-H bond activation. C-C bond formation of sp2 C-H activation is not covered in this review. The authors should specify this in the title and abstract section so make this clear.
- As we can see from this review, these sp3 C-H activation still heavily relies on directing group assists. Can the authors offer some insight of how the field should develop in this aspect as future directions?
Author Response
- [Comment #1]
This review only focuses on C(sp3)-H bond activation. C-C bond formation of C(sp2)-H activation is not covered in this review. The authors should specify this in the title and abstract section so make this clear.
[Response]
In fact, we described some examples of enantioselective functionalization of C(sp2)-H bonds, such as Scheme 7, 1) for C-C bond and 2) for C-N formation; Scheme 10, 2) for C-C formation; Scheme 11 for C-C bond formation; and Scheme 14, 2) for C-B bond formation. In order to avoid this misunderstanding, we have added underscore for each subtitles.
- [Comment #2]
As we can see from this review, these C(sp3)-H activations still heavily relies on directing group assists. Can the authors offer some insight of how the field should develop in this aspect as future directions?
[Response]
The development of non-covalent bond interaction between ligand and substrate controlled regioselective and enantioselective C-H functionalization as an excellent alternative way is attracting increasing attention in organic synthesis because this method not only free from the limitation of cyclometalation intermediate that reducing the reliance on directing group but also control the reaction-site at remote position. To best of our knowledge, only two examples were reported until now: 1) Phipps’ group developed an iron-pairing interaction controlled meta-selective and enantioselective C(sp2)-H borylation (SCIENCE, 2020, 367, 1246.) and 2) Sawamura’s group developed a hydrogen-bonding interaction controlled asymmetric remote C(sp3)-H borylation of amide (SCIENCE, 2020, 369, 970.). Therefore, developing another non-covalent bond interaction model and novel chiral ligands is also a challenge in this field, which should be the future direction.
Author Response File: Author Response.pdf
