{"title":"Theoretical mechanistic insights on the thermal and acid-catalyzed rearrangements of N-methyl-N-nitroanilines†","authors":"Shi Cheng , Chongjie Su , Tian Chen , Jiaxi Xu","doi":"10.1039/d4ob01449a","DOIUrl":null,"url":null,"abstract":"<div><div>The thermal and acid-catalyzed rearrangement mechanisms of <em>N</em>-methyl-<em>N</em>-nitroanilines were theoretically investigated <em>via</em> density functional theory (DFT) calculations for all possible proposed mechanisms. The results indicate that the thermal rearrangement of <em>N</em>-methyl-<em>N</em>-nitroanilines undergoes a radical pair complex mechanism through the homolysis of their N–N bond to generate a radical pair complex and the recombination of the radical pairs followed by aromatization. For the acid-catalyzed rearrangements, <em>N</em>-methyl-<em>N</em>-nitroanilines are first protonated on the nitrogen atom of their aniline moiety and then generate protonated <em>N</em>-methyl-<em>O</em>-nitroso-<em>N</em>-phenylhydroxylamines through a three-membered spirocyclic oxadiaziridine transition state. The <em>N</em>-protonated <em>N</em>-methyl-<em>O</em>-nitroso-<em>N</em>-phenylhydroxylamines favor homolytic dissociation to generate <em>N</em>-methylaniline cationic radical and nitrogen dioxide complexes, which further combine together and aromatize to afford protonated <em>N</em>-methyl-<em>o</em>-nitroanilines and <em>N</em>-methyl-<em>p</em>-nitroanilines, respectively. The radical pair complexes are more stable than the corresponding solvent-caged radical pairs. The thermal rearrangements require higher activation energy than the corresponding acid-catalyzed rearrangements.</div></div>","PeriodicalId":96,"journal":{"name":"Organic & Biomolecular Chemistry","volume":"22 46","pages":"Pages 9101-9112"},"PeriodicalIF":2.9000,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Organic & Biomolecular Chemistry","FirstCategoryId":"92","ListUrlMain":"https://www.sciencedirect.com/org/science/article/pii/S1477052024009194","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CHEMISTRY, ORGANIC","Score":null,"Total":0}
引用次数: 0
Abstract
The thermal and acid-catalyzed rearrangement mechanisms of N-methyl-N-nitroanilines were theoretically investigated via density functional theory (DFT) calculations for all possible proposed mechanisms. The results indicate that the thermal rearrangement of N-methyl-N-nitroanilines undergoes a radical pair complex mechanism through the homolysis of their N–N bond to generate a radical pair complex and the recombination of the radical pairs followed by aromatization. For the acid-catalyzed rearrangements, N-methyl-N-nitroanilines are first protonated on the nitrogen atom of their aniline moiety and then generate protonated N-methyl-O-nitroso-N-phenylhydroxylamines through a three-membered spirocyclic oxadiaziridine transition state. The N-protonated N-methyl-O-nitroso-N-phenylhydroxylamines favor homolytic dissociation to generate N-methylaniline cationic radical and nitrogen dioxide complexes, which further combine together and aromatize to afford protonated N-methyl-o-nitroanilines and N-methyl-p-nitroanilines, respectively. The radical pair complexes are more stable than the corresponding solvent-caged radical pairs. The thermal rearrangements require higher activation energy than the corresponding acid-catalyzed rearrangements.
期刊介绍:
Organic & Biomolecular Chemistry is an international journal using integrated research in chemistry-organic chemistry. Founded in 2003 by the Royal Society of Chemistry, the journal is published in Semimonthly issues and has been indexed by SCIE, a leading international database. The journal focuses on the key research and cutting-edge progress in the field of chemistry-organic chemistry, publishes and reports the research results in this field in a timely manner, and is committed to becoming a window and platform for rapid academic exchanges among peers in this field. The journal's impact factor in 2023 is 2.9, and its CiteScore is 5.5.