Photocatalytic Synthesis of 6-Phosphorylated Phenanthridines from 2-Isocyanobiphenyls via Radical C−P and C−C Bond Formation

Round 1

Reviewer 1 Report

In this manuscript, Ding and co-workers reported an efficient method for the preparation of 6-phosphorylated phenanthridines using low-cost Rose Bengal as catalyst and sustainable air as terminal oxidant under metal-free conditions at room temperature. Rose Bengal was found to be an available photocatalyst for the cascade phosphorylation cyclization of 2‑isocyanobiphenyls. A wide range of 6-phosphorylated phenanthridines have been synthesized efficiently via visible-light-induced radical addition cyclization under metal-free conditions. Therefore, I would like to recommend acceptance to Catalysts for publication as an article after some minor revisions.

1.     Some grammar and typo revisions: such as,

(1)  Introduction, “antileukaemic”, should be “antileukemic”;

(2)  Results and Discussion, “several organic photocatalysts” should be “several other organic photocatalysts”.

2.     The authors considered that the mechanism probably undergo cascade radical addition/cyclization processes. The corresponding references should be offered.

3.     Some of the products are known compounds, the references should be added.

4.     Introduction, the authors highlighted the advances for the synthesis of 6-position functionalized phenanthridines, some representative literatures should be cited.

5.     Is air the oxidant? The authors should try the reaction under inert atmosphere.

6.    In the part of “Characterization Data for Products 3” (Page 7, Line 133), of all the data you listed, there's no data about compound 3ca, you’d better check carefully and add it.

7.     In Scheme 2, have you considered the stereoselectivity of the reaction for compounds 3ca, 3fa, 3ga and 3ka?

English language is fine. 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

This manuscript by Ding et al describes a metal-free protocol for the synthesis of phosphorylated phenanthridines. This methodology could be an alternative way to the reported protocols to access these compounds and in my opinion could be published on Catalysts once the following issues are solved.

-Although the scope of the substitution in the biphenyl nucleus has been studied, the influence of electron-rich groups and ortho substitution in the R1 position are missing. Therefore, some of these substrates must be prepared and subjected to the reaction conditions.

-On the other hand, apparently all the tests have been carried out on a scale of 0.2 mmol. To further demonstrate the utility of the new methodology, experiments need to be performed with a 1 mmol and multigram scale.

A revision of the english language should be performed. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The revised manuscript by Ding et al have answered most of the questions and suggestions made by the reviewers. However, the experiment conducted with the model substrate at 6 mmol scale should be mentioned in the manuscript.

Once this issue has been solved, the manuscript could be published.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf