Coupling Reactions on Secondary Allylic, Propargylic, and Alkyl Carbons Using Organoborates/Ni and RMgX/Cu Reagents
Round 1
Reviewer 1 Report
This is a very interesting review on nickel cross-coupling reactions from one of the protagonists of this field. The manuscript of Yuichi Kobayashi fits well for the special issue devoted to the memory of Prof. Jiro Tsuji. The review is written perfectly. I consider that the manuscript can be published in Catalysts after response on the following minor remarks:
1. On page 6, line 139, the author mentions the carbonyl group in compound 32, however, it is not clear form Scheme 7. The “Functional Groups” should be described in this Scheme in detail.
2. On page 13, the structural formula of decarestrictin D (62) should be added to Scheme 15 for clarity.
3. “Summary” is too descriptive and resembles “Abstract”. The advantages of nickel catalysts over palladium ones in the reactions discussed, as well as reasons for the use of combinations of (alkyl)MgX and CuCN instead of borates for coupling of alkyl nucleophiles, should be added to the Summary.
Author Response
- On page 6, line 139, the author mentions the carbonyl group in compound 32, however, it is not clear form Scheme 7. The “Functional Groups” should be described in this Scheme in detail.
=> The section title "4.3. Functional group friendly ..." on page 5, line 223 has been changed to "4.3. Carbonyl group-friendly ..."
=> Furthermore, definition of FG has been added to Scheme 7 on page 6:
FG: CHO, C(=O)R, O(C=O)R
- On page 13, the structural formula of decarestrictin D (62) should be added to Scheme 15 for clarity.
=> Yes. The structure was added.
- “Summary” is too descriptive and resembles “Abstract”. The advantages of nickel catalysts over palladium ones in the reactions discussed, as well as reasons for the use of combinations of (alkyl)MgX and CuCN instead of borates for coupling of alkyl nucleophiles, should be added to the Summary.
=> “Summary” has been changed according to the above suggestion.
(original)
This review describes the nickel-catalyzed allylic coupling reactions of secondary allylic carbonates and esters with aryl and alkenyl borates possessing an alkanediol ligand such as 2,3-butanediol and 2,2-dimethyl-1,3-propanediol. These diol ligands are essential for achieving sufficient reactivity for the coupling reactions. The alkenyl borates were then used for the construction of dienes from less reactive allylic alcohol derivatives with bromine atom at the cisposition. Copper-based and copper-catalyzed substitutions of secondary allylic, propargylic, and alkyl substrates with RMgX are also presented. The application of these reactions for the synthesis of biologically active compounds is also discussed.
(revised)
Allylic coupling reactions of secondary allylic carbonates and esters with aryl and alkenyl borates was found to be catalyzed by nickel complexes such as NiCl2(PPh3)2 and NiCl2(dppf) and not by palladium catalysts. The alkanediol ligand on the borates was essential for producing high reactivity, which allowed the Ni-catalyzed coupling reaction between cyclopentenediol monoacetate 3 and borates. Furthermore, carbonyl group-friendly borates were synthesized from boronate esters and MeZnCl. Alkenyl borates were used for the construction of dienes from less reactive allylic alcohol derivatives with bromine atom at the cis position. In contrast to the aryl and alkenyl borates, reactive alkyl borates were not developed. Instead, substitutions on secondary carbons with RMgX under copper-based and copper-catalyzed conditions were studied to obtain the following results. The regioselectivity in the allylic substitution of cyclopentenediol monoacetate 3 was highly controlled by the ratio of RMgX/CuCN, halogen X (Cl, Br) in RMgX, and the solvent (Et2O vs. THF). The substitution of acyclic allylic picolinates proceeded with anti SN2' mode. Propargylic phosphates underwent propargylic substitution with RMgBr and a Cu catalyst in THF-DME. In addition, the recent success in the substitution of secondary alkyl (2-pyridine)sulfonates with RMgX is presented. The reactions have been applied for the synthesis of biologically active compounds.
Reviewer 2 Report
This review is an interesting, complete and passionate excursus on two kind of reactions extensively and brilliantly studied by prof. Kobayashi. I don't think any changes need to be made so the manuscript can be published directly and will be of interest to many readers.
Author Response
Correction was not provided. Thank you.Reviewer 3 Report
First of all, this manuscript covers the nickel-catalyzed allylic coupling reactions of secondary allylic carbonates and esters with aryl and alkenyl borates possessing an alkanediol ligand with appropriate and adequate references to related and previous work. It is a great topic, but I do think the title should be more specific in terms of what this paper is covering.
Secondly, the writings in this paper are very hard to understand and read, and I can see a lot of grammar mistakes. Besides, there are a lot of sentences, and expressions do not seem professional to me. For instance, On page 1, lines 36 to 37, “Later, I became interested in the allylic coupling of secondary allylic substrates with hard nucleophiles as a tool for making chiral carbon–carbon bonds and envisioned synthesis of biologically active compounds using them.” The author should probably revise this extra-long sentence because it’s tough to follow and disconnected in terms of meaning. I strongly suggest the author find a native speaker or someone else to revise most of the writing.
Thirdly, the structure of this manuscript is poorly organized, and I found it very hard to follow the logic behind it. This is probably partially because of some of those poor English expressions.
Lastly, although the references are adequate and appropriate, there are a lot of missing references that generally make this review hard to follow. For example, “1, Page 2, line 54, there’s no reference of this research.” And I have to check the origins of this research by myself. The author should make sure every citation is in the proper position.
Moreover, the font size in the tables is exaggeratedly big than the chemical equations and schemes, which makes the readers uncomfortable.
With all due respect to the authors, I cannot be supportive of this submission, but I can see how this work can be a comprehensive review in this area. I suggest the authors rewrite and reorganize the manuscript and probably resubmit this work to this journal later.
Author Response
First of all, this manuscript covers ..... I do think the title should be more specific in terms of what this paper is covering.
=> We changed the title:
(original) Coupling Reactions on Secondary Carbons using Organoborates and RMgX
(revised) Coupling Reactions on Secondary Allylic, Propargylic, and Alkyl Carbons using Organoborates/Ni and RMgX/Cu Reagents
Secondly, the writings in this paper are very hard to understand and read, and I can see a lot of grammar mistakes. Besides, there are a lot of sentences, and expressions do not seem professional to me. For instance, On page 1, lines 36 to 37, “Later, I became interested in ... using them.” ... I strongly suggest the author find a native speaker or someone else to revise most of the writing.
=> We changed “Later, I became interested in the allylic ..":
(revised) Later, the allylic substitution prompted me to investigate coupling reaction of secondary allylic substrates with hard nucleophiles to furnish chiral carbon–carbon bonds connecting various types of carbon groups.
(original) “Later, I became interested in the allylic coupling of secondary allylic substrates with hard nucleophiles as a tool for making chiral carbon–carbon bonds and envisioned synthesis of biologically active compounds using them.
=> Regarding to English writing:
We checked the review article carefully several times to revise sentences and paragraphs. Furthermore, the review thus changed was submitted to Editage, an English writing service, for further revision.
Thirdly, the structure of this manuscript is poorly organized, and I found it very hard to follow the logic behind it.
=> As mentioned above, the review was carefully revised.
Lastly, although the references are adequate and appropriate, there are a lot of missing references that generally make this review hard to follow. For example, “1, Page 2, line 54, there’s no reference of this research.”
=> This paragraph (page 2, line 106–118) is a summary of the first part of the review, and the references were not attached; instead, refs were cited in the following paragraphs in the original. However, ref numbers are attached to this paragraph.
Moreover, the font size in the tables is exaggeratedly big than the chemical equations and schemes, which makes the readers uncomfortable.
=> Font size in Tables 1, 2, 4, and 5 has been changed to 8 pt.
=> Font size in a small Table attached to Scheme 8, Table 3, and Table 6 has been changed to 12 pt, which become 8 pt after reduction in the text.
I suggest the authors rewrite and reorganize the manuscript and probably resubmit this work to this journal later.
=> As mentioned above, the manuscript was carefully revised along your comments and then English writing was corrected by Editage, one of English Editing Company.
Round 2
Reviewer 3 Report
The authors have addressed the previous comments appropriately and made relevant revisions. and in my view, the revised manuscript is suitable for publication in Catalysts.
