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Fundamentally, in hydrazine, the terminal-free N-center is more nucleophilic due to the \u03b1 effect, and this phenomenon is responsible for exhibiting the traditional copper\u2013allenylidene reactivity of EEC. In this work, we have described that, by switching the reactive nucleophilic N center via employing a protecting group strategy and diminishing the nucleophilicity via hydrogen bonding, allenal reactivity of EEC can be achieved. This copper-catalyzed protocol furnished medicinally important sterically congested unsymmetrical N-aryl pyrazoles in a highly regioselective manner (&amp;gt;20:1 rr) under mild conditions. In addition, valuable synthetic transformations and late-stage functionalization on the \u201cmethyl\u201d group have been performed to show the practical advantage of \u201cMe\u201d substitution on pyrazole. Further preliminary mechanistic investigation shed light on the course of the reaction sequence, e.g., in situ cyclization and methanol-assisted hydrolysis.<\/jats:p>","DOI":"10.1021\/acs.orglett.6c02604","type":"journal-article","created":{"date-parts":[[2026,7,21]],"date-time":"2026-07-21T18:46:41Z","timestamp":1784659601000},"page":"9736-9741","source":"Crossref","is-referenced-by-count":0,"title":["Cu-Catalyzed\nRegioselective Synthesis of Sterically\nCongested\n                    <i>N<\/i>\n                    -Aryl Pyrazoles Using a Traceless\nProtecting Group Strategy"],"prefix":"10.1021","volume":"28","author":[{"ORCID":"https:\/\/orcid.org\/0009-0001-6732-796X","authenticated-orcid":true,"given":"Soumalya","family":"Panja","sequence":"first","affiliation":[{"name":"Indian Institute of Science Education and Research Berhampur , , ,","place":["Berhampur, India, 760003"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8658-9295","authenticated-orcid":true,"given":"Pratap Kumar","family":"Mandal","sequence":"additional","affiliation":[{"name":"Indian Institute of Science Education and Research Berhampur , , ,","place":["Berhampur, India, 760003"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-3206-5935","authenticated-orcid":true,"given":"Subhra Kanti","family":"Mahato","sequence":"additional","affiliation":[{"name":"Indian Institute of Science Education and Research Berhampur , , ,","place":["Berhampur, India, 760003"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sumayya","family":"S","sequence":"additional","affiliation":[{"name":"Indian Institute of Science Education and Research Berhampur , , ,","place":["Berhampur, India, 760003"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-9151-5866","authenticated-orcid":true,"given":"Arijit","family":"Banerjee","sequence":"additional","affiliation":[{"name":"Indian Institute of Science Education and Research Berhampur , , ,","place":["Berhampur, India, 760003"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8792-4825","authenticated-orcid":true,"given":"Amit Kumar","family":"Simlandy","sequence":"additional","affiliation":[{"name":"Indian Institute of Science Education and Research Berhampur , , ,","place":["Berhampur, India, 760003"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2026,7,21]]},"reference":[{"key":"2026073109265781500_cit1","doi-asserted-by":"publisher","first-page":"101861","DOI":"10.1016\/j.jscs.2024.101861","article-title":"N-Arylpyrazole based Scaffolds: Synthesis and biological applications","volume":"28","author":"Akram","year":"2024","journal-title":"J. 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