1,4-Dihydropyrrolo[3,2-b]pyrroles with Two Embedded Heptagons via Alkyne Annulation
Gana Sanil1, Łukasz Dobrzycki2, Michał K Cyrański2
1Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
The Journal of Organic Chemistry
|December 31, 2024
Summary
Altering acidic catalysts reverses benzannulation reactions, forming two 7-membered rings from 1,4-dihydropyrrolopyrroles. This transformation occurs via a kinetically favored 6-endo-dig alkyne attack and vinyl shift.
Area of Science:
- Organic Chemistry
- Catalysis
- Reaction Mechanisms
Background:
- The double alkyne benzannulation reaction is a key synthetic route.
- Controlling the stereochemical outcome of cyclization reactions is crucial in organic synthesis.
Purpose of the Study:
- To investigate the effect of acidic catalysts on the benzannulation reaction of 1,4-dihydropyrrolopyrroles.
- To elucidate the mechanism of the observed product transformation.
Main Methods:
- Experimental investigation of the reaction under varying acidic conditions.
- Computational studies including density functional theory (DFT) calculations.
Main Results:
- Strong Brønsted acids were found to reverse the typical benzannulation pathway.
- The reaction yields two 7-membered rings instead of the usual products.
- Computational analysis supported a mechanism involving a 6-endo-dig attack and a 1,2-vinyl shift.
Conclusions:
- The nature of the acidic catalyst dictates the reaction's output.
- A novel pathway leading to 7-membered rings has been identified and mechanistically explained.
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