The Lloyd-Jones Research Group

Indium-mediated deoxygenation:
Synthesis of Homoallyl-substituted Vinylcyclopropanes

We recently discovered and then developed a novel (and unprecedented) reaction: the direct synthesis of homo-allyl-substituted vinyclyclopropanes from a,b-unsaturated ketones.

An example is shown above. This process delivers two crotyl units to dibenzylidene acetone and forms the corresponding vinylcyclopropane in 79% yield (on a 2.5g scale). Of a possible sixteen product isomers (±) the product shown comprises >50% of the product mixture. The reaction produces a single regioisomer (>98%) and this is 84% the cis cyclopropane diastereomer.

We have also been studying the diastereoselectivity of addition of crotyl indium to benzaldehyde in water versus organic solvents (particularly DMF). The results are suprising and a kinetic diastereoselection is observed.

References:

• "Homoallyl-substituted Vinylcyclopropanes from a,b-Unsaturated Ketones and Allylindium Derivatives", Henning A. F. Hoppe, Guy C. Lloyd-Jones*, Martin Murray, Torren M. Peakman and Kenneth E. Walsh, Angew. Chem. 1998, 37, 1545-1547.
• Regioselectivity and Diastereoselectivity in the Indium-mediated Homoallyl-Cyclopropanation of Dibenzylidene Acetone (dba)", Steven M. Capps, Torren M. Peakman, Guy C. Lloyd-Jones* Martin Murray and Kenneth E. Walsh, Tetrahedron Lett., 1998, 39, 2853-2856.
• "Kinetic Diastereoselection of Homoallylic Alkoxides: Syn crotylation of Arylaldehydes", Guy C. Lloyd-Jones* and Tim Russell, Synlett, in press.

This project is being funded by: A Young Organic Chemists Award (1997 - 1999) from the Zeneca Strategic Research Fund and an Industrial CASE studentship with Zeneca Agrochemicals 1998-2001.

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