Preparation and use of (2-butene-1,4-diyl) magnesium complexes in organic synthesis

A method for preparation of a fused ring carbocyclic alcohol 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, relative to SCE, 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 a carboxylic ester or acid halide in an ethereal or polyethereal solvent at a temperature of about 25.degree. C. or greater to form a fused ring carbocyclic alcohol.

A method for preparation of a carbocycle containing a .beta.,.gamma.-unsaturated ketone functionality 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, relative to SCE, 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 a carboxylic ester or acid halide in an ethereal or polyethereal solvent at a temperature of below -10.degree. C. to form a carbocycle containing a .beta.,.gamma.-unsaturated ketone functionality.

A method for preparation of a carbocyclic spirocycle containing a three-membered ring 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, relative to SCE, 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 a carboxylic ester or first acid halide in an ethereal or polyethereal solvent at a temperature of below -10.degree. C.;
• and
• (d) adding a second acid halide to form a carbocyclic spirocycle containing a three-membered ring.

A method for preparation of a keto-functionalized spirocarbocycle 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 relative to SCE, to form a highly reactive magnesium species;
• (b) contacting the highly reactive magnesium species with a cyclic hydrocarbon having 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 a bromoalkylnitrile in an ethereal or polyethereal solvent to form a keto-functionalized spirocarbocycle.