Tandem Gold-Catalyzed Dehydrative Cyclization/Diels–Alder Reactions: Facile Access to Indolocarbazole Alkaloids

A gold-catalyzed
synthesis of cyclic 2-oxodienes from readily prepared
propargyl alcohols and the subsequent Diels–Alder reaction
are reported. The dehydrative cyclization reactions proceeded smoothly,
and the dienes formed in situ were demonstrated to undergo cycloaddition
with a variety of dienophiles. This method offers a new strategy for
the synthesis of indolocarbazole alkaloids, whereby the convergent
synthetic design allows for differentiation between the indole nitrogens.