US 5,498,734 A · Preparation and use of (2-butene-1,4-diyl)magnesium complexes in organic synthesis

Abstract

The magnesium complexes of cyclic hydrocarbons containing conjugated dienes, such as 1,2-dimethylenecycloalkanes, and 1,3-butadienes, 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, alkylditriflates, bromoalkylnitriles, esters, or amides serve as a convenient method for synthesizing carbocyclic systems. Significantly, carbocycles prepared by this method contain functional groups such as the exocyclic double bond or a keto group in one of the rings which could be used for further elaboration of these molecules. Furthermore, fused bicyclic systems containing a substituted five-membered ring can be conveniently prepared at high temperatures by the reactions of (2-butene-1,4-diyl)magnesium complexes with carboxylic esters or acid halides whereas low temperatures lead to regioselective synthesis of .beta.,.gamma.-unsaturated ketones. Additionally, .gamma.-lactones, including spiro .gamma.-lactones, can be easily prepared in a one pot synthesis from the reaction of (2-butene-1,4-diyl)magnesium complexes with a ketone or aldehyde and carbon dioxide. Also, .delta.-lactones can be easily prepared in a one pot synthesis from the reaction of (2-butene-1,4-diyl)magnesium complexes with epoxides followed by reaction with CO.sub.2. Use of .alpha.-hydroxy epoxides without the addition of CO.sub.2 leads to the synthesis of vicinal diols. Chiral epoxides lead to chiral alcohols.

Claims28

Dependent claims

A method for the preparation of carbocycles 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-dyl)magnesium complex;
and
(c) contacting the (2-butene-1,4-diyl)magnesium complex with an electrophile to form a carbocycle.

1 more element

Dependencies are inferred from the claim text.

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

Life of this patent

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

Life of this patent

Abstract

Claims28