A unified strategy
for protecting-group-free synthesis of alkaloids
lennoxamine, chilenine, fumaridine, 8-oxypseudoplamatine, and 2-O-(methyloxy)fagaronine is reported. The core isoindolin-1-one
and isoquinolin-1-one structures were built by a silver-catalyzed
regio- and stereoselective cyclization of methyl 2-alkynylbenzimidates.
The regioselectivity of cyclization was achieved by utilizing the
intrinsic functionality of alkaloids.
Synthesis of a wide variety of 3‐amino‐1H‐inden‐1‐ones from N‐tert‐butyl‐2‐(1‐alkynyl)benzaldimines via intramolecular aminocarbonylation of alkynes using Cs2CO3 as catalyst and air as oxidant has been developed. This highly atom‐efficient, transition‐metal‐free reaction proceeds under thermal conditions. We propose that the reaction proceeds through an unprecedented 5‐exo‐dig cyclization of N‐tert‐butyl‐2‐(1‐alkynyl)benzaldimines and thermal rearrangement of 3‐methylene‐2λ2‐isoindolin‐1‐ols.
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