Pfau‐Plattner Azulene Synthesis

The preparation of azulene from cyclopentenocycloheptanone by the application of the ring expansion protocol is a multistep preparation involving the decomposition of diazoacetic ester, addition of the resulting carbene to indane, rearrangement of cycloheptatriene, hydrolysis of ester, decarboxylation, and dehydrogenation is known as the Pfau–Plattner azulene synthesis. This reaction has been amended by the direct addition of carbene generated from diazomethane, to indane. This reaction has a limited use in organic synthesis, perticullarlly for the azulene derivatives.