Synlett 2010(13): 1966-1968  
DOI: 10.1055/s-0030-1258499
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Efficient Synthesis of Novel Bridgehead-Substituted Bicyclo[3.2.1]octane-2,4-diones

Sebastian Wendeborn*, Hannes Nussbaumer, Jürgen Schaetzer, Tammo Winkler
Syngenta Crop Protection AG, Werk Stein, Schaffhauserstr., 4332 Stein, Switzerland
Fax: +41(62)8660860; e-Mail: sebastian.wendeborn@syngenta.com;
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Publikationsverlauf

Received 4 March 2010
Publikationsdatum:
16. Juli 2010 (online)

Abstract

We report the efficient synthesis of bridgehead-substituted bicyclo[3.2.1]octane-2,4-diones. The key step in their construction is a highly efficient intramolecular [3+2] cycloaddition between a nitrile oxide and an olefin. The reductive ring cleavage of the resulting dihydroisoxazole provides the desired bridgehead-­substituted bicyclo[3.2.1]octane-2,4-diones.

15

Compounds 7, 18, and 19 exist preferentially in the diketone form in CDCl3, as observed by ¹H NMR. However, in a more polar solvent system (CDCl3-CD3OD, 10:1) two isomeric keto-enol tautomers are observed for compound 20 (see Supporting Information for details).