Preparation and use of (2-butene-1,4-diyl)magnesium complexes in organic synthesis
AssigneeBoard of Regents of the University of Nebraska
InventorReuben D. Rieke
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Abstract
The magnesium complexes of cyclic hydrocarbons, such as 1,2-dimethylenecycloalkanes, are readily prepared in high yields using highly reactive magnesium. Reactions of these (2-butene-1,4-diyl)magnesium reagents with electrophiles such as dibromoalkanes, alkylditosylates, or bromoalkylnitriles serve as a convenient method for synthesizing spirocyclic systems. Significantly, spirocarbocycles prepared by this The present invention was made with Government support under Contract No. GM35153 awarded by the National Institute of Health. The Government has certain rights in the invention.
Claims20
A method for the preparation of spirocycles comprising:
- a. contacting a magnesium(II) salt in an ethereal, polyethereal, or hydrocarbon solvent with a reducing agent having a reduction potential of about -1.5 volts, or more negative, to form a highly reactive magnesium species;
- b. contacting the highly reactive magnesium species with a cyclic hydrocarbon containing at least two conjugated exocyclic double bonds to form a (2-butene-1,4-diyl)magnesium complex;
- and
- c. contacting the (2-butene-1,4-diyl)magnesium complex with an electrophile to form a spirocycle.
A method for the preparation of spirocycles comprising:
- a. contacting a magnesium(II) salt in an ethereal, polyethereal, or hydrocarbon solvent with an alkali metal salt of an aromatic anion to form a highly reactive magnesium species;
- b. contacting the highly reactive magnesium species with a cyclic hydrocarbon containing at least two conjugated exocyclic double bonds to form a (2-butene-1,4-diyl)magnesium complex;
- and
- c. contacting the (2-butene-1,4-diyl)magnesium complex with an electrophile at a temperature below about 100.degree. C. to form a spirocycle.
A method for the preparation of spirocycles comprising:
- a. contacting a magnesium(II) salt in an ethereal, polyethereal, or hydrocarbon solvent with a reducing agent having a reduction potential of about -1.5 volts, or more negative, to form a highly reactive magnesium species, wherein the reducing agent is an alkali metal salt of an aromatic anion;
- b. contacting the highly reactive magnesium species with a cycloalkane containing at least two conjugated exocyclic double bonds to form a (2-butene-1,4-diyl)magnesium complex;
- and
- c. contacting the (2-butene-1,4-diyl)magnesium complex with an electrophile selected from the group consisting of organodihalides, organoditosylates, haloalkylnitriles, esters, and amides to form a spirocycle.
Dependencies are inferred from the claim text.