Synthesis 2004(2): 298-307  
DOI: 10.1055/s-2003-44360
FEATUREARTICLE
© Georg Thieme Verlag Stuttgart · New York

Cascade Cyclization via a 4-exo-dig-Cyclocarbopalladation for an Easy Access to New Polycyclic Structures

Bahaâ Salem, Philippe Klotz, Jean Suffert*
Faculté de Pharmacie, Université Louis Pasteur de Strasbourg (UMR 7081 CNRS/ULP), 74 Route du Rhin 67401 Illkirch Cedex, France
Fax: +33(3)90244310; e-Mail: jeansu@aspirine.u-strasbg.fr;
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Publikationsverlauf

Received 23 September 2003
Publikationsdatum:
09. Dezember 2003 (online)

Abstract

The 5-exo-dig-cyclocarbopalladation is a known reaction although the functionality present on the substrates used is generally limited. This reaction was performed on our original substrates propargylic diols 2a-c and 3a-c gave encouraging results. Once the analogs α-bromopropargylic diols were used, the 4-exo-dig-cyclocarbopalladation turns out to be a new possible way to prepare bicyclic compounds containing a strained 1,2-cyclobutanediol. This process is associated with a Stille cross-coupling that can be ended in some cases by a 6π-electrocyclization. This reaction sequence can thus achieve an increase in structural complexity from readily available starting materials, in a one-pot operation.

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In presence of Pd(PPh3)4, the process was unsucessfully when carried out in polar solvents e.g. THF, DMF, NMP and CH3CN.