page_title: Robinson annulation
section_title: Asymmetric Robinson annulation
hierarchical_section_title: Robinson annulation / Scope and variations / Asymmetric Robinson annulation
caption_attribution_description: English: Fig. 3: Organocatalytic tandem Michael-aldol reaction for the one-pot synthesis of chiral thiochromenes
context_page_description: The Robinson annulation is a chemical reaction used in organic chemistry for ring formation. It was discovered by Robert Robinson in 1935 as a method to create a six membered ring by forming three new carbon–carbon bonds. The method uses a ketone and a methyl vinyl ketone to form an α, β-unsaturated ketone in a cyclohexane ring by a Michael addition followed by an aldol condensation. This procedure is one of the key methods to form fused ring systems.
  Formation of cyclohexenone and derivatives are important in chemistry for their application to the synthesis of many natural products and other interesting organic compounds such as antibiotics and steroids. Specifically, the synthesis of cortisone is completed through the use of the Robinson annulation.
  The initial paper on the Robinson annulation was published by William Rapson and Robert Robinson while Rapson studied at Oxford with professor Robinson. Before their work, cyclohexenone syntheses were not derived from the α, β-unsaturated ketone component. Initial approaches coupled the methyl vinyl ketone with a naphthol to give a naphtholoxide, but this procedure was not sufficient to form the desired cyclohexenone.
context_section_description: Asymmetric synthesis of Robinson annulation products most often involve the use of a proline catalyst. Studies report the use of L-proline as well as several other chiral amines for use as catalysts during both steps of the Robinson annulation reaction. The advantages of using the optically active proline catalysis is that they are stereoselective with enantiomeric excesses of 60–70%.
  Wang, et al. reported the one-pot synthesis of chiral thiochromenes by such an organocatalytic Robinson annulation.
caption: Organocatalytic tandem Michael-aldol reaction for the one-pot synthesis of chiral thiochromenes
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