Approach to the blues: A highly flexible route to the azulenes
(Chemical Equation Presented) A palette of blues: Chlorobicyclo-[5.3.0] decatrienones are readily prepared from cycloheptatrienes by cycloaddition of dichloroketene, ring expansion with a diazoalkane, and dehydrochlorination in dimethylformamide. These compounds are used as intermediates in the regiocontrolled synthesis of a wide variety of natural and nonnatural azulenes (see scheme).
Carret, Sebastien,Blanc, Aurelien,Coquerel, Yoann,Berthod, Mikael,Greene, Andrew E.,Depres, Jean-Pierre