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Pure Appl. Chem., Vol. 72, No. 9, pp. 1745-1756, 2000.

 

 

Bicyclopropylidene. A unique tetrasubstituted alkene and versatile C6-building block for organic synthesis*

Armin de Meijere**, Sergei I. Kozhushkov, Thomas Späth, Malte von Seebach, Sandra Löhr, Hanno Nüske, Tim Pohlmann, Mazen Es-Sayed, and Stefan Bräse

Institut für Organische Chemie der Georg-August-Universität Göttingen, Tammannstrasse 2, D-37077 Göttingen, Germany

Abstract: Bicyclopropylidene (4), now readily available in preparatively viable quantities, is evolving as a useful C6 building block for organic synthesis due to its enhanced reactivity at the C-H, the C=C, as well as both types of C-C single bonds. Monosubstituted derivatives are accessible by deprotonation/electrophilic substitution. Di- and tetrasubstituted bicyclopropylidenes are best made by copper-mediated reductive dimerization of bromolithiocarbenoids. The 1,3-dipolar cycloadducts of nitrones rearrange to spirocyclopropanated piperidones, palladium-catalyzed codimerizations with acrylates occur with opening of one of the rings to yield precursors to bicyclo[3.3.0]octene and bicyclo[5.3.0]decene skeletons. Silicon-heteroatom bonds can be added across the double bond of 4 under palladium catalysisjust like across a CC triple bond, and carbopalladation of the double bond in 4 occurs more rapidly than that in an acrylate. A variety of new three-component reactions of 4 with alkenyl as well as aryl halides and dienophiles have been developed and extended to be carried out in a combinatorial sense, even on a polymer support, with an additional dimension added in the cleavage step. Most of the reported reactions of bicyclopropylidene (4) proceed with good to excellent yields.

*Lecture presented at the 13th International Conference on Organic Synthesis (ICOS-13), Warsaw, Poland, 1-5 July 2000.
** Corresponding author

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