Asymmetric Organocatalytic 1,3-Dipolar Cycloaddition of Azomethine Ylides with β-Substituted Cyclic Enones
Han Zhong1, Xiao-Yi Zhang1, Yong-Mou Yao1
1The Fifth Affiliated Hospital and Key Laboratory of Molecular Target & Clinical Pharmacology, School of Pharmaceutical Sciences, Guangzhou Medical University, Xinzao, Panyu District, Guangzhou 511436, China.
Abstract:
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-a]phthalazine derivatives 3 through vinylogous iminium ion activation by combining a cinchona-based primary amine C3 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-a]phthalazin-10(8H)-one derivatives 4 with excellent stereocontrol via endo-dienamine activation.
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