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.
Abstract:
Drastic changes to the character of the acidic catalyst enable the reversal of the double alkyne benzannulation reaction output. In the presence of a strong Brønsted acid, 1,4-dihydropyrrolopyrroles undergo transformation which results in the formation of two 7-membered rings. Computational studies imply that the thermodynamically unfavored 7-membered ring is forged via the kinetically favored 6-endo-dig attack of a protonated alkyne at the position 3a of pyrrolopyrrole followed by a 1,2-vinyl shift.
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