Page 58 - Read Online
P. 58
Page 22 of 54 Yang et al. Chem Synth 2023;3:7 https://dx.doi.org/10.20517/cs.2022.38
Scheme 27. Organocatalyzed Mannich/cyclization reaction of isothiocyanato thiobutyrolactone 48 with alkylidene pyrazolones 54.
This figure is used with permission from the Royal Society of Chemistry [81] .
Butyrolactone-derived cyclic imino esters as C-N-C synthons
The asymmetric 1,3-dipolar cycloaddition of azomethine ylides with electron-deficient olefins is one of the
highly powerful methods for the synthesis of various highly substituted pyrrolidine scaffolds widespread in
natural compounds. Recently, novel spirocyclic butyrolactone skeletons with multiple stereocenters could
be constructed through simple 1,3-dipolar cycloadditions between butyrolactone-derived cyclic imino esters
57 as azomethine ylide precursors and electron-deficient species as dipolarophiles with suitable
organocatalysts [Scheme 28].
