Enantioselective Synthesis of Unsymmetrical Diaryl‐Substituted Spirocyclohexanonepyrazolones through a Cascade [4+2] Double Michael Addition
The spirocyclic pyrazolones are an important class of molecular structures with significant biological and pharmaceutical activities. Herein, we demonstrate that the combination of a Cinchona‐based chiral primary amine and an ortho‐fluorobenzoic acid is an efficient catalyst system for the double Michael addition of arylidenepyrazolones with α,β‐unsaturated ketones, providing chiral unsymmetrical 6,10‐diaryl‐substituted spiro[cyclohexanone‐pyrazolone] derivatives in high yields (up to 98%) with good diastereoselectivities and excellent enantioselectivities (up to 88:12 dr, 99% ee).
Document Type: Research Article
Affiliations: Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, People's Republic of China, Fax: (+86)-512-6588-0378
Publication date: 2013-03-11