The Effect of Base and Nucleophile on the Nucleophilic Substitution of Methoxytropone Derivatives: An Easy Access to 4- and 5-Substituted Multifunctional Azulenes.

The nucleophilic substitution on 3-substituted 2-methoxytropones to form azulenes is dependent on the nucleophile and base employed. With bulkier nucleophiles (ethyl/methyl cyanoacetate), the reaction proceeds with the abnormal nucleophilic substitution irrespective of the base and with smaller nucleophiles (malononitrile), the reaction follows base-dependent normal and abnormal nucleophilic substitution. Thus, the methodologies are developed to selectively obtain 4- and 5-substituted azulenes based on the nature of bases and nucleophiles employed.