DABCO-catalyzed unusual [4 + 2] cycloaddition reaction: non-substituted allenoate acts as a four-carbon synthon and facile synthesis of spirooxindoles

A DABCO-catalyzed domino reaction between methyleneoxindoles and allenoates which enables the direct synthesis of spirooxindoles is reported. This is the first example of a non-substituted allenoate to act as a four-carbon synthon in a tertiary amine-catalyzed reaction.