Multicomponent Diastereoselective Synthesis of Indolizidines via 1,3-Dipolar Cycloadditions of Azomethine Ylides

The synthesis of polyfunctionalized indolizidines from pipecolinic acid alkyl ester derivatives, aldehydes and a wide range of dipolarophiles by multicomponent 1,3-dipolar cycloadditions is developed in a diastereoselective manner. The cycloadditions take place in toluene with short reaction times at 70 °C, giving good yields. The synthesis of these fused heterocycles is also studied starting from pipecolinic acid, generating the dipole through a decarboxylative route at 120 °C. The relative configuration of the resulting products as well as the mechanistic pathways are also explained.The Spanish Ministerio de Ciencia e Innovación (MICINN) (projects CTQ2010-20387, and Consolider Ingenio 2010, CSD2007-00006), the Spanish Ministerio de Economia y Competitividad (MINECO) (projects CTQ2013-43446-P and CTQ2014-51912-REDC), FEDER, the Generalitat Valenciana (PROMETEO 2009/039 and PROMETEOII/2014/017), and the University of Alicante. L. C. M. thanks Spanish Government for a fellowship