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.