Geminal Repulsion Disrupts Diels–Alder Reactions of Geminally Substituted Cyclopentadienes and 4H-Pyrazoles
We have experimentally and computationally explored the sluggish Diels-Alder reactivities of the geminally substituted 5,5-dimethylcyclopentadiene and 5,5-dimethyl-2,3-diazacyclopentadiene (4,4-dimethyl-4H-pyrazole) scaffolds. We found that geminal dimethylation of 1,2,3,4-tetramethylcyclopentadiene...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Elsevier BV
2022
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| Online Access: | https://hdl.handle.net/1721.1/141238 |
| _version_ | 1811075769048236032 |
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| author | Levandowski, Brian J Abularrage, Nile S Raines, Ronald T |
| author_facet | Levandowski, Brian J Abularrage, Nile S Raines, Ronald T |
| author_sort | Levandowski, Brian J |
| collection | MIT |
| description | We have experimentally and computationally explored the sluggish Diels-Alder reactivities of the geminally substituted 5,5-dimethylcyclopentadiene and 5,5-dimethyl-2,3-diazacyclopentadiene (4,4-dimethyl-4H-pyrazole) scaffolds. We found that geminal dimethylation of 1,2,3,4-tetramethylcyclopentadiene to 1,2,3,4,5,5-hexamethylcyclopentadiene decreases the Diels-Alder reactivity towards maleimide by 954-fold. Quantum mechanical calculations revealed that the decreased Diels-Alder reactivities of gem-dimethyl substituted cyclopentadienes and 2,3-diazacyclopentadienes are not a consequence of unfavorable steric interactions between the diene and dienophile as reported previously, but a consequence of the increased repulsion within the gem-dimethyl group in the transition state. The findings have implications for the use of cyclopentadienes in "click" chemistry. |
| first_indexed | 2024-09-23T10:11:35Z |
| format | Article |
| id | mit-1721.1/141238 |
| institution | Massachusetts Institute of Technology |
| language | English |
| last_indexed | 2024-09-23T10:11:35Z |
| publishDate | 2022 |
| publisher | Elsevier BV |
| record_format | dspace |
| spelling | mit-1721.1/1412382022-03-17T03:31:23Z Geminal Repulsion Disrupts Diels–Alder Reactions of Geminally Substituted Cyclopentadienes and 4H-Pyrazoles Levandowski, Brian J Abularrage, Nile S Raines, Ronald T We have experimentally and computationally explored the sluggish Diels-Alder reactivities of the geminally substituted 5,5-dimethylcyclopentadiene and 5,5-dimethyl-2,3-diazacyclopentadiene (4,4-dimethyl-4H-pyrazole) scaffolds. We found that geminal dimethylation of 1,2,3,4-tetramethylcyclopentadiene to 1,2,3,4,5,5-hexamethylcyclopentadiene decreases the Diels-Alder reactivity towards maleimide by 954-fold. Quantum mechanical calculations revealed that the decreased Diels-Alder reactivities of gem-dimethyl substituted cyclopentadienes and 2,3-diazacyclopentadienes are not a consequence of unfavorable steric interactions between the diene and dienophile as reported previously, but a consequence of the increased repulsion within the gem-dimethyl group in the transition state. The findings have implications for the use of cyclopentadienes in "click" chemistry. 2022-03-16T18:04:15Z 2022-03-16T18:04:15Z 2021 2022-03-16T17:59:27Z Article http://purl.org/eprint/type/JournalArticle https://hdl.handle.net/1721.1/141238 Levandowski, Brian J, Abularrage, Nile S and Raines, Ronald T. 2021. "Geminal Repulsion Disrupts Diels–Alder Reactions of Geminally Substituted Cyclopentadienes and 4H-Pyrazoles." Tetrahedron, 91. en 10.1016/J.TET.2021.132160 Tetrahedron Creative Commons Attribution-NonCommercial-NoDerivs License http://creativecommons.org/licenses/by-nc-nd/4.0/ application/pdf Elsevier BV PMC |
| spellingShingle | Levandowski, Brian J Abularrage, Nile S Raines, Ronald T Geminal Repulsion Disrupts Diels–Alder Reactions of Geminally Substituted Cyclopentadienes and 4H-Pyrazoles |
| title | Geminal Repulsion Disrupts Diels–Alder Reactions of Geminally Substituted Cyclopentadienes and 4H-Pyrazoles |
| title_full | Geminal Repulsion Disrupts Diels–Alder Reactions of Geminally Substituted Cyclopentadienes and 4H-Pyrazoles |
| title_fullStr | Geminal Repulsion Disrupts Diels–Alder Reactions of Geminally Substituted Cyclopentadienes and 4H-Pyrazoles |
| title_full_unstemmed | Geminal Repulsion Disrupts Diels–Alder Reactions of Geminally Substituted Cyclopentadienes and 4H-Pyrazoles |
| title_short | Geminal Repulsion Disrupts Diels–Alder Reactions of Geminally Substituted Cyclopentadienes and 4H-Pyrazoles |
| title_sort | geminal repulsion disrupts diels alder reactions of geminally substituted cyclopentadienes and 4h pyrazoles |
| url | https://hdl.handle.net/1721.1/141238 |
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