A three-component, general and practical route for diastereoselective synthesis of aza-spirocyclic pyrazolones <i>via</i> a decarboxylative annulation process
An efficient, general, and practical route for highly diastereoselective synthesis of aza-spirocyclic pyrazolones from easily available α-amino acids, aldehydes, and alkylidene pyrazolones by means of a decarboxylative annulation process is reported. This high-yielding reaction proceeds through a [3+2]-cycloaddition reaction between alkylidene pyrazolones and a nonstabilized azomethine ylide generated