Synfacts 2009(1): 0052-0052  
DOI: 10.1055/s-0028-1087404
Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions
© Georg Thieme Verlag Stuttgart ˙ New York

Stereocontrolled Synthesis of Highly Substituted Tetrahydropyrans

Contributor(s): Mark Lautens, Frédéric Ménard
K. Tadpetch, S. D. Rychnovsky*
University of California, Irvine, USA
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Publikationsverlauf

Publikationsdatum:
18. Dezember 2008 (online)

Significance

A Re(VII) complex catalyzed the highly selective condensation of easily accessible starting materials using a very mild and simple protocol to give densely functionalized tetrahydropyrans 3 (THP). Aromatic aldehyde partners 2 give a single diastereomer where all substituents are equatorially oriented. Whereas aliphatic aldehydes give diastereomeric mixtures (4 and 5), ­alkenyl aldehydes provide an alternative, as illustrated by complex THP 11. Achieving high atom-efficiency, the catalytic Prins cyclization reported improves previous protocols using excess acid (the conjugate base moiety is generally incorporated into the THP at the end of the reaction).