Pentafulvenes are a unique class of compounds that originally attracted attention due to their propensity to display nonbenzenoid aromaticity. Subsequently, they were recognized as valuable synthons for the construction of a wide range of compounds by virtue of their ability to display multiple cycloaddition profiles. Naturally, this area of organic chemistry has experienced rapid growth over the last five decades, fueled by elegant work showcasing the unique reactivity of pentafulvenes in a plethora of cycloaddition reactions. In this Review, we have attempted to provide a systematic account of the methods for the generation of pentafulvenes, their rich and varied cycloaddition chemistry, organometallic reactions, and theoretical studies that support their versatility. Further, we have highlighted their applications in the synthesis of a variety of complex structural frameworks. It is our conviction that this Review will be useful to a wide range of chemists, and will spur further research in this promising area.

A bonding moment: A new cobalt‐ or manganese‐catalyzed amination of azoles has been developed using peroxide and an acid additive to couple various types of azoles with ammonia, and primary or secondary amines (see scheme). The catalyst loadings are low, the optimal reaction conditions are mild, and the substrate scope is broad. The product azoles are an important pharmacophore of high biological activity.

Toss an amine into the ring: A new metal‐free protocol for the amination of oxazoles has been developed by using iodobenzene diacetate to couple various oxazoles with amines (see scheme). The reaction proceeds through a ring‐opening and subsequent ring‐closing pathway. The optimal conditions are very mild and the substrate scope is broad, producing a range of 2‐aminooxazoles, an important pharmacophore with high bioactivity.