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Additions of Silyl Enol Ethers to β-Formyl Esters - a Chelate-controlled Synthesis of the Pheromone (+)-Eldanolide

✍ Scribed by Angert, Hubert ;Czerwonka, Regina ;Reißig, Hans-Ulrich

Publisher
John Wiley and Sons
Year
2006
Tongue
English
Weight
466 KB
Volume
1996
Category
Article
ISSN
0947-3440

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✦ Synopsis

Abstract

Chelate‐controlled Mukaiyama reaction of silyl enol ethers 2a, 2b, 2c, and 2d with β‐formylcarboxylate 1 in the presence of TiCl~4~ provided γ‐lactones 3a, 3b, 3c, and 3d in very good yields and with good to excellent trans selectivities. The use of BF~3~, SnCl~4~, and SnBr~4~ as Lewis acids afforded 3a with moderate cis selectivity thus excluding chelate control. Starting with (S)‐1 TiCl~4~‐promoted reaction with 2b, we obtained optically active γ‐lactone 3b which was efficiently converted into the pheromone (+)‐eldanolide in two steps. The enantiomeric excess of 87% proved that the sequence proceeds without detectable racemization.

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