Pseudo-multicomponent 1,3-dipolar cycloaddition involving metal-free generation of unactivated azomethine ylides.

ABSTRACT

The pseudo-multicomponent reaction between propargyl amine, an aldehyde and an electron-deficient alkene is described. The C-H activation takes place thermally and allows the obtaining of cycloadducts in very good yields with high diastereoselectivities. The relative configuration is determined by X-ray diffraction analysis of the chiral molecule, obtained as a single diastereoisomer, using a chiral maleimide. A brief study of the stability of the possible ylides involved in the process is also mentioned, confirming the high diastereoselectivity observed. The high functional group density of these cycloadducts permits the synthesis of complex heterocycles. After allylation or propargylation of the pyrrolidine nitrogen atom, RCM-DA cycloaddition or cyclotrimerization with an alkyne is studied, respectively. In this last example, the resulting tetracyclic structures are of potential interest as drugs for the treatment of cystic fibrosis.