A concise synthesis of (±)-cuparene via Grignard, trimethylaluminum and dimethyltitanium dichloride (Reetz Alkylation) reactions to form the quaternary centers of (±)-cuparene is reported.
A general protocol for conversion of a tetrasubstituted alkene to a highly methylated hydrocarbon is tested with a concise synthesis of the natural product, herbertene. The conversion: alkene ® 1,2-diol ® 1,2-dimethylated hydrocarbon should find application in a number of synthesis designs.
A two part organic laboratory experiment illustrating the Grignard reaction and the concept of kinetic versus thermodynamic control is described. The reaction of phenylmagnesium bromide with 2-methylcyclopentanone yileds an unsymmetrical benzylic alcohol which can be dehydrated using toluenesulfonic acid to give predominately the less substituted alkene. Application of heat to the reaction mixture over a period of two hours reverses the trend to give the more substituted alkene as the major product in 91% relative yield. The dehydration is monitored by GC/MS and the experiment can be performed using macro and microscale techniques.
