Advanced Application of Planar Chiral Heterocyclic Ferrocenes

Round 1

Reviewer 1 Report

The authors provided a review on the catalytic activity and selectivity of ferrocene ligands in various reactions including reduction of ketones, hydrogenation of olefins, hydroboration, cycloaddition, enantioselective synthesis of biaryls, Tsuji-Trost allylation. A prospect of the economic strategies for stereodivergent synthesis of new planar chiral ferrocene derivatives and recyclable catalysts was given. This review is of great importance and should be accepted and publishes in inorganic after minor revision: 

1. Prof. Xumu Zhang and coworkers developed some important ferrocene ligands such as f-amphox, fampha, f-amphol and f-amphamide and the corresponding iridium catalysts, which could promote the reduction of various ketones with high TON (up to 1,000,000), excellent conversion (＞99%) and enantioselectivity (＞99% ee ). I think Zhang’s work should be reviewed.

2. Some important literatures should be cited:

1) Org. Lett., 2016, 18, 2938. (f-amphox)

2) Chem. Sci. 2016, 7, 6669-6673. (Wudaphos)

3) Chem-Eur, J., 2017, 23, 970. (f-amphol)

4) Org. Lett., 2017, 19, 690. (f-ampha)

5) Chinese Journal of Chemistry, 2018, 36, 851. (f-amphamide)

6) J. Org. Chem., 2018, 83, 10749. (f-diaphas)

   7) Org. Chem. Front., 2021, 8, 6830–6836. (SPIROL-derived PPFAPhos)

Author Response

Dear Reviewer,

We would like to thank the reviewer for thoughtful comments and efforts towards improving our manuscript. The text of the manuscript was corrected according the reviewer comments. The language was improved throughout the manuscript.

1. The work of W. Wu et al. (Org. Lett. 2016, 18, 2938–2941) was cited in the manuscript since it devoted to the application of chiral heterocyclic derivatives of ferrocenes (Scheme 17, reference 51). Other references were cited in Introduction (ref. 10, 11, 17-20).

Sincerely yours, Prof. Irina A. Utepova

Author Response File: Author Response.docx

Reviewer 2 Report

The review is a summary of recent work conducted in the field of asymmetric catalysis using transition metal complexes with ferrocene ligands. It is split into seven sections, the first six dealing with organic transformations and the last one being dedicated to enantiomer resolution. The time period it covers stretches to the beginning of the century with the coverage of the work of the groups of Hou and Dai on asymmetric allylation reaction using planar-chiral phosphinoferrocene oxazolines. The authors include several new entries to this topic. Nevertheless, the work done in this field in the first decade of the century has been extensively reviewed in the past. See for instance

Chiral Ferrocenes in Asymmetric Catalysis: Synthesis and Applications, Dai, L.-X.; Hou, X.-L., Eds., John Wiley & Sons, Ltd, 2009.

Arrayás, R. G.; Adrio, J.; Carretero, J. C., Recent Applications of Chiral Ferrocene Ligands in Asymmetric Catalysis, Angew. Chem. Int. Ed. 2006, 45, 7674-7715.

Dai, L.-X.; Tu, T.; You, S.-L.; Deng, W.-P.; Hou, X.-L., Asymmetric Catalysis with Chiral Ferrocene Ligands, Acc. Chem. Res. 2003, 36, 659-667.

I suggest that the readers should be pointed toward a piece of this literature should they desire a review that precedes this one.

Each of the seven sections is concluded with a small summary. However, these summaries lack any references. I suggest that cross-references to already mentioned literature are also included in these summaries so that they are easier for the reader to follow.

The language of the paper is somewhat cumbersome and hard-to-read. I attach a copy of the manuscript with some sections that need editing (in my opinion) highlighted, some with my suggestions. I believe that changes in this regard would help readability as well as clarity of the text. An overarching problem is the extensive use of gerunds instead of nouns. Additionally, I would strongly suggest that the authors refrain from the use of the term ”fragment” in the way they sometimes do and use the terms “moiety“, „substituent“, „functional group“ or „pendant group“ instead.

My additional suggestions to improve the clarity include:

On the line 319, it should be specified which group of ligands and which types of reactions the authors are referring to.

The beginning of the paragraph, that starts on the line 452, is cumbersome. Different word choice and order could bring more clarity.

The label on the line 573 should read “Scheme 41“ instead of “Scheme 42“. The label of the compound 188 in this scheme on the line 572 is out of alignment with the other labels.

In the text on the line 578 in the brackets, it should read “Scheme 42“ instead of “Scheme 41“.

The paragraph that starts on the line 682 needs to have references added to it.

I would recommend to consider the acceptance of this review after necessary language corrections if these remarks are addressed.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

We would like to thank the reviewer for thoughtful comments and efforts towards improving our manuscript. These comments helped us to significantly improve the manuscript. The text of the manuscript was corrected according the reviewer comments.

1. We understand the reviewer desire to separate the asymmetric hydroboration in a section, but there are few examples of these reactions proceeding in the presence of planar chiral heterocyclic ferrocene derivatives. Therefore, we kindly ask the reviewer to keep this example unchanged (Scheme 15, ref. 44, 45).
2. Undoubtedly, before this work the groups of Hou and Dai have made a great contribution on asymmetric allylation reaction using planar-chiral phosphinoferrocene oxazolines. Therefore, the corresponding references were cited in Introduction (ref. 16, 21, 22).
3. The cross-references of already mentioned literature were included in small summaries for each of the seven sections.
4. The language was improved throughout the manuscript.
5. In the conclusion of the second section (on the line 319 in PDF file) the group of ligands and types of reactions were specified. Cross-references were added.
6. The beginning of the paragraph (after Scheme 32, line 452 in PDF file) was corrected according the reviewer comments.
7. The label of scheme in the section 5 (Annelation and cycloaddition, line 573 in PDF file) was corrected. It was written “Scheme 41“ instead of “Scheme 42“. The label of the compound 188 in scheme 41 was alignment with the other labels.
8. In the text (line 578 in PDF file) in the brackets, “Scheme 41“ was replaced on “Scheme 42“.
9. In conclusion of the section 6 (line 682 in PDF file) the corresponding references were added.

Sincerely yours,

Prof. Irina A. Utepova

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Authors addressed my suggestions in an extent that is satisfactory for me. 

I recommend to accept the paper after only minor spelling and language corrections with following suggested changes: 

line 22 subsequent

line 121 sterically

line 181 of the initial

line 182 affected

line 333 decrease

line 426 olefin moiety

line 536 silanol moiety

line 598 diphenylphosphine substituent

line 661 diphenylphosphine substituent

Author Response

Dear Reviewer,

We would like to thank the Reviewer for time and effort. We have made the appropriate spelling and language corrections according to Reviewer comments.

1. The mistake on line 22 was corrected. The “subsiquent" was replaced on “subsequent”.
2. On line 121 the “steric" was replaced on “sterically”.
3. On line 181 the “of an initial" was replaced on “of the initial”.
4. On line 182 the “effected" was replaced on “affected”.
5. On line 333 the “decreasing" was replaced on “decrease”.
6. On line 426 the “olefin" was replaced on “olefin moiety”.
7. On line 536 the “silanol" was replaced on “silanol moiety”.
8. On line 598 the “diphenylphosphine" was replaced on “diphenylphosphine substituent”.
9. On line 661 the “diphenyl phosphine" was replaced on “diphenylphosphine substituent”.

Sincerely yours,

Prof. Irina A. Utepova

Author Response File: Author Response.docx