Asymmetric Organocatalytic 1,3-Dipolar Cycloaddition of Azomethine Ylides with β-Substituted Cyclic Enones.

The enantioselective and diastereoselective control of 1,3-dipolar cycloaddition reactions to β-substituted cyclic enones has been developed. The 1,3-dipolar cycloaddition of phthalazinium dicyanomethanides with cyclic dienones affords chiral tetrahydropyrrolo[2,1-]phthalazine derivatives through vinylogous iminium ion activation by combining a cinchona-based primary amine and a chiral camphorsulfonic acid additive. Conversely, with a weaker 3,5-bis(trifluoromethyl)benzoic acid additive, the 1,3-dipolar cycloaddition of phthalazinium dicyanomethanides with β-substituted cyclic enones leads to chiral hexahydroisoindolo[1,2-]phthalazin-10(8)-one derivatives with excellent stereocontrol via -dienamine activation.