Review Reports

Round 1

Reviewer 1 Report

The topic of the review concerning Palladium and Copper Catalyzed Sonogashira reaction is quite important. Unfortunately, the review is not comprehensive: latest papers published in 2019 were not included in the review for some reason; also there is no explanation why authors chose 17 years to be collected. Very strange and even unscientific classification of the material was used in the review – by the years of appearance of papers in the journals. It means that authors did not analyze the results published in the papers, and simply enumerated them. Thus, the review loses its scientific value and becomes useless for chemists working in this area. The abstract is unsuccessful, especially the second sentence.

Many other shortcomings were found in the review.

There are many excessive reactions given in the review - synthesis of starting compounds and further reactions of the compounds 10, 18, 33, 34, 65, 67, 99, 104, 201. Many references concerning the utility of the particular classes of organic compounds are old and unnecessary, see for example, references 18-20, 32, 33, 38, 41, 43, 47, 49, 50, 52, 53, 57, 66, 75-78, 82, 83, 87-89, 93, 97-99, 102, 135, 140, 141. There is a mess in many references 44, 79, 63, 65, 71, 84-86, 90-113, 115 etc, some authors mentioned in the text of the review are not present in the list of authors of papers. Schemes were drawn in different styles (see, for example, Schemes 20, 21, 32 and others. Yields of the target products were not given in the Schemes, which makes it difficult to assess the effectiveness of the methods. No references were given for Shemes 51 and 52; the results presented in Scheme 14 were not discussed in the text. There are many mistakes in the list of references 1-4, 8-10, 64, 110, 113. English should be improved; there are many misprints, poor choice of words and mistakes in the text and Schemes.

Taking in account all above-listed shortcomings, the paper should be rejected for publication in journal Catalysts.

Author Response

Reviewer 1

The topic of the review concerning Palladium and Copper Catalyzed Sonogashira reaction is quite important. Unfortunately, the review is not comprehensive: latest papers published in 2019 were not included in the review for some reason; also there is no explanation why authors chose 17 years to be collected.

A: The work on review was started in 2018 and we gathered data upto 2018. When paper was submitted the year 2019 was not complete that’s why its data is not entered. Also Sufficient data not available for years 2018 and 2019 specifically.

Very strange and even unscientific classification of the material was used in the review – by the years of appearance of papers in the journals. It means that authors did not analyze the results published in the papers, and simply enumerated them. Thus, the review loses its scientific value and becomes useless for chemists working in this area.

A: The mode of classification is yearly because purpose of review is to elaborate the year wise progress of Palladium and Copper Catalyzed Sonogashira Cross Coupling. The mode of classification on catalysts and ligands is a known pattern. The catalyst was also specified in the title. The use of words 17 years in title lost its importance if we change its classification mode.

The abstract is unsuccessful, especially the second sentence.

A: The abstract has been revised thoroughly

There are many excessive reactions given in the review - synthesis of starting compounds and further reactions of the compounds 10, 18, 33, 34, 65, 67, 99, 104, 201. 

A: The product of Sonogashira is also used as intermediate in many reactions that’s why reactions are long. And in many reactions the halide portion of the compound was synthesized that’s why reactant have many steps.

Many references concerning the utility of the particular classes of organic compounds are old and unnecessary, see for example, references 18-20, 32, 33, 38, 41, 43, 47, 49, 50, 52, 53, 57, 66, 75-78, 82, 83, 87-89, 93, 97-99, 102, 135, 140, 141.

A: The background related to compound or ligand used was given in the review that’s why use these references to show from where related data was taken.

There is a mess in many references 44, 79, 63, 65, 71, 84-86, 90-113, 115 etc, some authors mentioned in the text of the review are not present in the list of authors of papers.

A: These are checked and revised.

Schemes were drawn in different styles (see, for example, Schemes 20, 21, 32 and others.

A: These are checked and revised.

Yields of the target products were not given in the Schemes, which makes it difficult to assess the effectiveness of the methods.

A: The yields of the available compounds have been added.

No references were given for Schemes 51 and 52;

A: Refrences have been incorporated.

The results presented in Scheme 14 were not discussed in the text.

A: The results for scheme 14 have been incorporated in text section.

There are many mistakes in the list of references 1-4, 8-10, 64, 110, 113.

A: These are checked and revised.

English should be improved; there are many misprints, poor choice of words and mistakes in the text and Schemes.

A: English language has been revised and grammar mistakes have been removed.

Reviewer 2 Report

The following words were recommended to rewrite as follows.
Line 25: "organic complexes" is "so on."

It is recomended to rewrite the text of "Conclusion" as follows.
In summary, Sonogashira cross-coupling is used for the synthesis of different organic bioactive and pharmacologically important compounds. This review article highlighted the palladium and copper-based catalysts for Sonogashira cross-coupling. The Pd–Cu-atalyzed cross-coupling of terminal acetylenes with sp2-C halides is a broadly useful method for conjugated acetylenes. Especially, the search of the more reactive and long-living catalysts for the aryl chlorides remains to be a challenging object for future research.

Author Response

Reviewer 2

The following words were recommended to rewrite as follows. Line 25: "organic complexes" is "so on."

A: The suggested changes have been incorporated

It is recomended to rewrite the text of "Conclusion" as follows. 
In summary, Sonogashira cross-coupling is used for the synthesis of different organic bioactive and pharmacologically important compounds. This review article highlighted the palladium and copper-based catalysts for Sonogashira cross-coupling. The Pd-Cu-catalyzed cross-coupling of terminal acetylenes with sp2-C halides is a broadly useful method for conjugated acetylenes. Especially, the search of the more reactive and long-living catalysts for the aryl chlorides remains to be a challenging object for future research.

A: The suggested changes have been incorporated in conclusion.

Reviewer 3 Report

This manuscript provides a well-balanced selection of interesting examples showcasing the use of Sonogashira cross-coupling reactions to bring about the synthesis of new C-C bonds. This reaction is as stated a very important method in organic chemistry and the widespread use is testament to this. 

In their manuscript the authors highlight several examples demonstrating different approaches to achieve the Sonogashira coupling. At this point the structuring of the manuscript that simply devides sections as in the year a publication was reported appears very odd making this read more like a chronicle rather than a valuable sorce of information. It would be worth considering alternative approaches to structure this work, e.g. by presenting different motifs generated (yne-ones, aryl-alkynes, ene-ynes etc.) or the type and nature of catalyst (homogeneous/heterogeneous; copper-free etc.). 

The authors provide schemes for each example presented and in many cases use color-coding to highlight the alkyne moiety. Some schemes appear skewed and with varying drawing settings such as size of structures drawn; this should be made more uniform. It is also recommended to concistently include the yield in each scheme for the key step.

The biggest weakness of the manuscript in the current form is the poor language and grammar/syntax. It is highly recommended to employ a native speaker to bring this to the necessary level. Numerous mistakes severely hamper the quality and readability of the manuscript.

Finally, this type of review will require a more in-depth conclusion section to clearly summarise the standing of this field (specific transformation) and provide direction to open questions or unsolved problems that arise from this review. If this is not included, a mere compiling of examples is achieved without presenting any insight in remaining challenges and the bigger picture with regards to sustainability and the future relevance of this catalytic transformation.

 

Author Response

Reviewer 3

In their manuscript the authors highlight several examples demonstrating different approaches to achieve the Sonogashira coupling. At this point the structuring of the manuscript that simply devides sections as in the year a publication was reported appears very odd making this read more like a chronicle rather than a valuable sorce of information. It would be worth considering alternative approaches to structure this work, e.g. by presenting different motifs generated (yne-ones, aryl-alkynes, ene-ynes etc.) or the type and nature of catalyst (homogeneous/heterogeneous; copper-free etc.). 

A: The mode of classification is yearly because purpose of review is to elaborate the year wise progress of Palladium and Copper Catalyzed Sonogashira Cross Coupling. The mode of classification on catalysts and ligands is a known pattern. The catalyst was also specified in the title. The use of words 17 years in title lost its importance if we change its classification mode.

The authors provide schemes for each example presented and in many cases use color-coding to highlight the alkyne moiety. Some schemes appear skewed and with varying drawing settings such as size of structures drawn; this should be made more uniform. It is also recommended to concistently include the yield in each scheme for the key step.

A: These are checked and revised.

The biggest weakness of the manuscript in the current form is the poor language and grammar/syntax. It is highly recommended to employ a native speaker to bring this to the necessary level. Numerous mistakes severely hamper the quality and readability of the manuscript.

A: The manuscript has been thoroughly revised and grammar mistakes have been removed

Finally, this type of review will require a more in-depth conclusion section to clearly summarise the standing of this field (specific transformation) and provide direction to open questions or unsolved problems that arise from this review. If this is not included, a mere compiling of examples is achieved without presenting any insight in remaining challenges and the bigger picture with regards to sustainability and the future relevance of this catalytic transformation.

A: The conclusion section has been revised

Round 2

Reviewer 1 Report

The authors did not address the most important shortcomings 1-3 and 8. The authors ' explanations on these points are not convincing. Therefore, I think that the paper should be rejected for publication in journal Catalysts.