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The University of Southampton
Chemistry

Research project: Whitby: Insertion of carbenoids into organozirconocene chlorides

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Carbenoid insertions into organozirconocene chlorides are particularly valuable when the product is readily further elaborated.

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An example is the convergent route to functionalised allylmetallic species 2 which react readily with carbonyl compounds.[1]

 

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It is important that in the intermediate allylzirconium reagent 2, the metal is localised at one end of the allyl-system to ensure good regioselectivity of further reactions. An example is the insertion of cyclopropyl carbenoids 4 to produce allylzirconium species 5 which may be elaborated to either alkylidene cyclopropanes 6 or vinylcyclopropanes 7.[2] The species 6 and 7 are of established use in a variety of tandem reactions where the strain of the cyclopropyl ring is used to drive transformations. 

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We often discover unusual rearrangements, and unexpected routes to useful species when investigating new chemistry. For example insertion of most lithiated epoxides 8 into organozirconium species affords alkenes 9 via the expected epoxide ring opening and dealkoxymetallation.[3] However, insertion of lithiated sulphonyl epoxides into alkenylzirconocene chlorides follows a different path to afford the very useful regiodefined metal enolates 9 or 10.[4]

Carbenoid insertion into alkenylzirconocenes - a convergent synthesis of functionalised allylmetallics, Kasatkin, A. N.; Whitby, R. J. Tetrahedron Lett. 2000, 41, 6211-6216.
Cyclopropyl carbenoid insertion into alkenylzirconocenes - a convergent synthesis of alkenylcyclopropanes and alkylidenecyclopropanes, Thomas, E.; Kasatkin, A. N.; Whitby, R. J. Tetrahedron Lett. 2006, 47, 9181-9185.
Insertion of metallated epoxynitriles into organozirconocene chlorides. A convergent synthesis of 2-cyano-1,3-dienes, Kasatkin, A. N.; Whitby, R. J. Tetrahedron Lett. 2000, 41, 6201-6205.
A convergent regiospecific synthesis of zirconium enolates, Kasatkin, A.; Whitby, R. J. Tetrahedron 2003, 59, 9857-9864.

Related research groups

Organic Chemistry: Synthesis, Catalysis and Flow
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