Aldol Reaction – Simple Diastereoselectivity Cis gives Syn

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Cis Lithium enolates (Z) generally give Syn Aldol products

In an aldol reaction, cis enolates prefer to form syn aldols. The reaction proceeds via a chair-like transition state where the aldehyde chooses to react with the methyl group equatorial. As the enolate has no choice over its orientation, only a syn product is possible.

C. H. Heathcock, C. T. Buse, W. A. Kleschick, M. C. Pirrung, J. E. Sohn and J. Lampe, J. Org. Chem., 1980, 45, 1066–1081.

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