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Synfacts 2013; 9(3): 0285
DOI: 10.1055/s-0032-1318258
Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions
© Georg Thieme Verlag Stuttgart · New York

Mimicking Nature: Enantioselective Cationic Polyene Cyclization

Contributor(s):
Mark Lautens
,
Harald Weinstabl
Schafroth MA, Sarlah D, Krautwald S, Carreira EM * ETH Zürich, Switzerland
Iridium-Catalyzed Enantioselective Polyene Cyclization.

J. Am. Chem. Soc. 2012;
134: 20276−20278
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Further Information

Publication History

Publication Date:
15 February 2013 (online)

 
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Key words

polycyclization - iridium - zinc triflate - polyenes

Significance

The biogenic isoprene rule, established in 1955 by Ruzicka, Eschenmoser, and Stork (Helv. Chim. Acta 1955, 38, 1890; J. Am. Chem. Soc. 1955, 77, 5068), stimulated biomimetic studies for the construction of polycyclic frameworks, like the steroid skeleton. Approaches based on Brønsted/Lewis acid catalysis (Yamamoto, Loh, Corey), organocatalysis (Ishihara, MacMillan, Jacobsen), and transition-metal catalysis (Takeuchi, Helmchen, Hartwig) are reported.


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Comment

The authors report the development of a highly enantioselective polycyclization method using the combination of Lewis acid activation with iridium-catalyzed allylic substitution. This strategy relies on direct use of branched, racemic allylic alcohols and furnishes a diverse and unique set of carbo- and heteropolycyclic ring systems in good yield and ≥99% ee.


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