A strategy to functionalized spiro[4.5]trienones,
by domino silver-catalyzed
decarboxylative acylation or alkylation/ ipso-cyclization
of N-arylpropiolamides with α-keto acids/alkyl
carboxylic acids, is presented. This transformation offers a wide
range of substituted 3-acyl/alkyl-spiro[4.5]trienones in high yields
with a broad substrate scope. The approach was further extended to
access fused tricyclic frameworks, 6,7-dihydro-3H-pyrrolo[2,1-j]quinoline-3,9(5H)-diones.
A domino propargylation/furanylation
(intramolecular exo-dig-cyclization)/benzannulation
reaction of 2,4-diyn-1-ols
with 1,3-dicarbonyl compounds has been developed for the first time.
This provides a novel and effective method for the preparation of
aryl/heteroaryl-fused benzofurans from easily accessible starting
materials in a single step. The methodology was extended to pyrrolyl-benzannulation
to obtain aryl/heteroaryl-fused indoles. Further, application of this
approach in the synthesis of eustifoline D and dictyodendrin structural
frameworks has been demonstrated.
Arylative annulation of 2-carbonyl-3-propargyl indoles with boronic acids under sequential palladium/triflic acid catalysis is described. The present strategy to provide di-and triaryl carbazoles in one pot involves benzannulation through difunctionalization of alkynes. The strategy showed a good substrate scope with respect to boronic acids as well as 2-carbonyl-3-propargyl indoles to afford the corresponding carbazoles in decent yields.
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