Access to Indole- And
Pyrrole-Fused Diketopiperazines
via Tandem Ugi-4CR/Intramolecular Cyclization and Its Regioselective
Ring-Opening by Intermolecular Transamidation
posted on 2016-02-20, 06:01authored byShashi Pandey, Shahnawaz Khan, Awantika Singh, Harsh
M. Gauniyal, Brijesh Kumar, Prem M. S. Chauhan
An efficient approach for the synthesis of indole- and
pyrrole-fused
diketopiperazines has been developed. This protocol involves the Ugi
four-component reaction (U-4CR) followed by an intramolecular cyclization
of the Ugi products at room temperature to afford the desired products
in good to excellent yields. In addition, it is interesting to report
the subsequent regioselective ring-opening of diketopiperazine unit
occurring via an intermolecular transamidation reaction under mild
condition, resulting in the formation of highly functionalized indole-2-carboxamides
and pyrrole-2-carboxamides.