AlCl<sub>3</sub>‑Promoted
Selective Michael
Addition with Allenoate and Methyleneindolinone: Synthesis of Spirocyclic
Oxindole by Using Allenoate as a Four-Carbon Component Building Block
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Abstract
The AlCl<sub>3</sub>-promoted cyclization
of readily available
allenoates with methyleneindolinone is disclosed. The present strategy
provides a rapid access to spirocyclic oxindole-cyclohexenones in
an efficient manner. Remarkably, the allenoate is implemented as a
four-carbon (4C) component to form the ring, which shows high synthetic
efficiency. Flexibility of this method allows quick synthesis of spirocyclic
oxindole-dihydropyrans by varying one of the components. It is also
noteworthy that AlCl<sub>3</sub> serves as the chlorine source as
well as an effective catalyst to facilitate this interesting transformation