The decomposition of diazodicarbonyl compounds in the
presence
of various metal catalysts has become a reliable method for the functionalization
of indoles via carbenoid intermediates. Exploiting the nucleophilic
reactivity of the in situ generated malonic ester product formed,
we herein report a tandem C–H functionalization/Conia-ene cyclization
of N-alkyne tethered indoles. This double functionalization
of diazodicarbonyls generates a range of pyrrolo[1,2-a]-, pyrido[1,2-a]-, and azepino[1,2-a]indole products with good synthetic efficiency.
Indolyl
α-diazocarbonyl compounds have proven to be effective
starting materials for the construction of various 2,3-ring fused
indole frameworks. Activation of the diazo functional group under
metal catalysis generates a spiro-cyclic indolenine-type intermediate
which rearranges to provide two distinct carbazoles upon oxidation.
The current study investigates the effects of the catalyst as well
as the substituents on the migratory group involved in controlling
the selectivity of the rearrangement.
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