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A thioarylation method is developed for the synthesis of 2,3-dihydrothiopheniums through an electrophilic-cyclization–cross-coupling mechanism, harnessing the gold(I)/(III) cycle of the recently developed MeDalPhosAuCl catalyst. Single-crystal X-ray crystal structural analysis of the dihydrothiophenium products characterized the anti-addition of the sulfur and Csp2 group to the alkyne and a preference for 5-endo dig cyclization. The dihydrothiophenium products are demonstrated as synthetic building blocks for stereodefined acyclic tetrasubstituted alkenes upon ring-opening reaction with amines. Intramolecular competition experiments show the favorability of Csp3 tether cyclizations over Csp2 tethers, preferentially generating dihydrothiopheniums over thiopheniums. Intermolecular competition experiments of alkyne aryl groups and an intermolecular aryl iodide competition suggest a rate-determining reductive elimination step in the gold(I)/gold(III) catalytic cycle. This rate-determining step is further supported by HRMS analysis of reaction intermediates that identify the catalyst resting state under turnover conditions. Catalyst poisoning experiments provide evidence of substrate inhibition, further consistent with these conclusions.
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Synthesis of 1,3-Diaryltriazenes and Azo Dyes from Aryl Amines Using N-Nitrososulfonamides
Abstract New methods for the synthesis of 1,3-diaryltriazenes and azo dyes from aryl amines are reported. Both methods involve the formation of aryl diazonium intermediates via the transnitrosation of aryl amines with N-nitrososulfonamides. Each two-step transformation may be performed in one reaction vessel at room temperature with no precautions taken to exclude air or moisture. Several triazene and azo dye structures are reported here for the first time, demonstrating the utility of operating the two-step reaction sequence under mild conditions.
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- Award ID(s):
- 1752821
- PAR ID:
- 10426576
- Date Published:
- Journal Name:
- Synlett
- Volume:
- 34
- Issue:
- 08
- ISSN:
- 0936-5214
- Page Range / eLocation ID:
- 963 to 969
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1055/a-1969-4050
