Abstract:

Electrondeficient nitroalkenes exhibit different reactivities in organic synthesis. For example: i) act as dienophiles reacting with dienes to afford nitrocycloadducts derivatives in Diels-Alder reaction; ii) as 1,3-dipolarophiles (DPP) reacting with several 1,3-dipoles in [3+2] cycloadditions and iii) as heterodienes (HD), often in the presence of Lewis acid, to afford cyclic alkyl nitronates in hetero-Diels- Alder reactions. To the best of our knowledge, there are only two examples of the use of chiral nitroalkenes in stereoselective tandem [4+2]/[3+2] cycloadditions. Recently, we synthesized non-racemic nitroalkenes 3-5 from L-alanine, L-phenylalanine and L-leucine, respectively in five steps and 80-90% overall yield. Theses electrondeficient nitroalkenes have exhibited excellent stereochemical stability, reactivity and diastereoselectivity in a great number of different reactions. In order to increase the scope of the reactivity of 3-5 herein we investigate the reactivity and diastereoselectivity these new “chirons” in tandem intermolecular [4+2]/[3+2] cycloadditions employing Li+ containing catalysts.