New Methods For Stereocontrolled Cycloaddition/Dearomatization Reactions Under Catalytic Conditions

Our group has previously developed ferrocenyl-proline ligands that incorporate planar and central chirality. This feature makes them suitable for a particularly efficient simultaneously chiral induction. In fact, they have shown excellent diastereo- and enantioselectivity in [3+2] cycloaddition reactions between azomethine ylides and electron deficient alkenes.[1] Buchner[2] discovered in 1885 a route for the functionalization of benzene employing diazo compounds to provide a carbene moiety. Since then, the use of diazo compounds has been the most developed method for the metal mediated carbene transfer to C-C double bonds.[3] This reaction provides a very useful method for the convergent formation of cyclopropanes. These [2+1] cycloadducts constitute attractive target molecules in natural products and bioorganic chemistry.[4] In the present work stereoselective [2+1] reactions between fused hetero polyaromatic rings and different diazo compounds are described, in which ligands LP-1 to LP-5 constitute the source of chirality. [1] Conde, E.; Bello, D.; de Cozar, A.; Sanchez, M.; Vazquez, M. A.; Cossio, F. P. Chem. Sci. 2012, 3, 1486-1491. [2] Buchner, E.; T. Ber. Dtsch. Chem. Ges. 1885, 18, 2377. [3] Maas, G. Chem. Soc. Rev., 2004, 33, 183-190. [4] (a) Kirkland, T.A; Colucci, J.; Geraci, L. S.; Marx, M.A.; Schneider, M.; Kaelin, D.E; Martin, S.F. J. Am. Chem. Soc., 2001, 123, 12432-12433; (b) Chen, D. Y. K.; Pouwer, R. H.; Richard, J. A. Chem.Soc.Rev., 2012, 41, 4631-4642; (c) Ozuduru G.; Schubach, T.; Boysen M. M. K. Org, Lett., 2012, 14 (19), 4990-4993.