Multicomponent Reactions of Diazoamides: Diastereoselective Synthesis of Mono- and Bis-spirofurooxindoles

This paper describes the intermolecular generation of carbonyl ylides by dirhodium(II) tetraacetate-catalyzed reaction of 3-diazoindol-2-ones in the presence of aryl aldehydes and heteroaryl aldehydes.
These carbonyl ylides were subsequently trapped with dipolarophiles such as dimethyl acetylenedicarboxylate, maleic anhydride, and ethyl acrylate to afford spirofurooxindoles. Consequently,
diastereoselective synthesis of spirodihydrofurooxindoles through the multicomponent reactions
of cyclic diazoamides was successfully achieved for the first time. The stereochemistry of the
spirofurooxindole is unequivocally corroborated by the single-crystal X-ray analysis of the
representative product 4o. Interestingly, these reactions were extended to double multicomponent
reactions of bis-cyclic diazoamides to afford the respective complex polycycles in a tandem manner,
which led to the construction of four carbon−carbon bonds, two carbon−oxygen bonds, and four
chiral centers in a single synthetic step.