A Ring Expansion-Annulation Strategy for the Synthesis of Substituted Azulenes.Preparation and Suzuki Coupling Reactions of 1-Azulenyl riflates

摘要

A new strategy for the synthesis of substituted azulenes is reported,based on the reaction of #beta#'-bromo-#alpha#-diazo ketones with rhodium carboxylates.The key transformation involves intramolecular addition of a rhodium carbenold to an arene #pi#-bond,electrocyclic ring opening,#beta#-elimination,Tautomerization,and trapping to produce 1-hydroxyazulene derivatives.The synthetic utility of the method is enhanced by the ability of the triflate derivtives to participate in Suzuki coupling reactions.as illustrated in a synthesis of the antiulcer drug engualen sodium (DT1-32).