Tropolone

Tropolone is an organic compound with the formula C₇H₅(OH)O. It is a pale yellow solid that is soluble in organic solvents. The compound has been of interest to research chemists because of its unusual electronic structure and its role as a ligand precursor. Although not usually prepared from tropone, it can be viewed as its derivative with a hydroxyl group in the 2-position.

Synthesis and reactions

Many methods have been described for the synthesis of tropolone. One involves bromination of 1,2-cycloheptanedione with N-bromosuccinimide followed by dehydrohalogenation at elevated temperatures and by acyloin condensation of the ethyl ester of pimelic acid the acyloin again followed by oxidation by bromine.

The compound readily undergoes O-alkylation to give cycloheptatrienyl derivatives, which in turn are versatile synthetic intermediates. With metal cations, it undergoes deprotonation to give chelate complexes, e.g., Cu(O₂C₇H₅)₂.

Occurrence

Many natural products contain the tropolone skeleton. These include puberulic acid, stipitatonic acid, stipitatic acid, puberulonic acid,and sepedonin. It arises via a polyketide pathway, which affords a phenolic intermediate that undergoes ring expansion.