NHC-catalyzed [4 + 2] annulations of allenoates and 2,3-dioxopyrrolidine derivatives

Abstract

A facile NHC-catalyzed [2+4] annulation of allenoates with 2,3-dioxypyrrolidine derivatives was discovered, which paved a new avenue to the construction of highly substituted pyranopyrrole with moderate to good yields, high...

NHC-catalyzed formal [3 + 3] annulations of δ-acetoxy allenoates for the synthesis of 4H-pyran derivatives

“…Based on the previous reports, 12,15,17 a possible reaction mechanism was proposed. As illustrated in Scheme 5, the NHC precursor N6 reacts with the base to generate the active NHC catalyst N6′ which then reacts with 1a to form the cationic intermediate I .…”

“…14 Recently, various transformations reported by our group showed unique regioselectivities in NHC catalyzed transformations of allenoates. 15 According to the abovementioned analysis, we find that the characterization of allenoates and Lewis base catalysts can both lead to different reactivities. Therefore, the NHC catalyzed diverse transformations of allenoates are urgently needed and valuable.…”

“…To the best of our knowledge, the NHC catalyzed transformations of δ-acetoxy allenoates are rare and have not been fully developed. To continue our study on NHC-promoted transformations of allenoates and further explore the unique catalytic potential of NHC in the reactions involving allenoates, 15 we herein report an NHC catalyzed [3 + 3] cycloaddition reaction of δ-acetoxy allenoates and 1C,3O-bisnucleophiles (Scheme 1e).…”