Chonghe Zhang, Robert J Gilliard, Christopher Cummins
{"title":"Arene extrusion as an approach to reductive elimination at boron: Implication of carbene-ligated haloborylene as a transient reactive intermediate","authors":"Chonghe Zhang, Robert J Gilliard, Christopher Cummins","doi":"10.1039/d4sc05524a","DOIUrl":null,"url":null,"abstract":"Herein, we report a boron-centered arene extrusion reaction to afford putative cyclic(alkyl)(amino) carbene (CAAC)-ligated chloroborylene and bromoborylene. The borylene precursors, chloro-boranorbornadiene (ClB(C<small><sub>6</sub></small>Me<small><sub>6</sub></small>), <strong>2</strong><small><sup>Cl</sup></small>) and bromo-boranorbornadiene (BrB(C<small><sub>6</sub></small>Me<small><sub>6</sub></small>), <strong>2</strong><small><sup>Br</sup></small>) were synthesized through the reaction of the corresponding 1-halo-2,3,4,5-tetramethylborole dimer (XBC<small><sub>4</sub></small>Me<small><sub>4</sub></small>)<small><sub>2</sub></small> (X = Cl, <strong>1</strong><small><sup>Cl</sup></small>; X = Br, <strong>1</strong><small><sup>Br</sup></small>) with 2-butyne. Treatment of <strong>2</strong><small><sup>Cl</sup></small> with CAACs resulted in the release of di-coordinate chloro-borylene (CAAC)BCl from hexamethylbenzene (C<small><sub>6</sub></small>Me<small><sub>6</sub></small>) at room temperature. In contrast, the reaction of <strong>2</strong><small><sup>Br</sup></small> with CAAC led to the formation of a boronium species [(CAAC)BC<small><sub>6</sub></small>Me<small><sub>6</sub></small>]<small><sup>+</sup></small>Br<small><sup>–</sup></small> (<strong>7</strong>) at room temperature. Heating <strong>7</strong> in toluene promoted the release of di-coordinate bromo-borylene (CAAC)BBr as a transient species. Surprisingly, heating <strong>7</strong> in dichloromethane resulted in the C–H activation of hexamethylbenzene. The conversion of a CAAC-stabilized bromo-borepin to a borylene, a boron-centered retro Büchner reaction, was also investigated.","PeriodicalId":9909,"journal":{"name":"Chemical Science","volume":null,"pages":null},"PeriodicalIF":7.6000,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Chemical Science","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1039/d4sc05524a","RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Herein, we report a boron-centered arene extrusion reaction to afford putative cyclic(alkyl)(amino) carbene (CAAC)-ligated chloroborylene and bromoborylene. The borylene precursors, chloro-boranorbornadiene (ClB(C6Me6), 2Cl) and bromo-boranorbornadiene (BrB(C6Me6), 2Br) were synthesized through the reaction of the corresponding 1-halo-2,3,4,5-tetramethylborole dimer (XBC4Me4)2 (X = Cl, 1Cl; X = Br, 1Br) with 2-butyne. Treatment of 2Cl with CAACs resulted in the release of di-coordinate chloro-borylene (CAAC)BCl from hexamethylbenzene (C6Me6) at room temperature. In contrast, the reaction of 2Br with CAAC led to the formation of a boronium species [(CAAC)BC6Me6]+Br– (7) at room temperature. Heating 7 in toluene promoted the release of di-coordinate bromo-borylene (CAAC)BBr as a transient species. Surprisingly, heating 7 in dichloromethane resulted in the C–H activation of hexamethylbenzene. The conversion of a CAAC-stabilized bromo-borepin to a borylene, a boron-centered retro Büchner reaction, was also investigated.
期刊介绍:
Chemical Science is a journal that encompasses various disciplines within the chemical sciences. Its scope includes publishing ground-breaking research with significant implications for its respective field, as well as appealing to a wider audience in related areas. To be considered for publication, articles must showcase innovative and original advances in their field of study and be presented in a manner that is understandable to scientists from diverse backgrounds. However, the journal generally does not publish highly specialized research.