(Hetero)aromatics from dienynes, enediynes and enyne–allenes

Abstract

The construction of aromatic rings has become a key objective for organic chemists. While several strategies have been developed for the functionalization of pre-formed aromatic rings, the direct construction of an aromatic core starting from polyunsaturated systems is yet a less explored field. The potential of such reactions in the formation of aromatics increased at a regular pace in the last few years. Nowadays, there are reliable and well-established procedures to prepare polyenic derivatives, such as dienynes, enediynes, enyne-allenes and hetero-analogues. This has stimulated their use in the development of innovative cycloaromatizations. Different examples have recently emerged, suggesting large potential of this strategy in the preparation of (hetero)aromatics. Accordingly, this review highlights the recent advancements in this field and describes the different conditions exploited to trigger the process, including thermal and photochemical activation, as well as the use of transition metal catalysis and the addition of electrophiles/nucleophiles or radical species.

Rhodium-catalysed tetradehydro-Diels–Alder reactions of enediynes via a rhodium-stabilized cyclic allene

“…An advanced strategy for preparing functionalized aromatic rings is cycloaromatisation of polyunsaturated acyclic building blocks, including, enediynes, enyne-allenes and dienynes. 1 The tetradehydro-Diels-Alder (TDDA) reaction of polyunsaturated enediyne systems is of particular note as it allows for the direct formation of a benzenoid ring in a single step, via an intriguing high energy cyclic allene intermediate, which typically aromatises via a hydride shi (Scheme 1a). 2,3 The thermal mode of this reaction has been investigated for many years, but its synthetic applications are severely limited by the requirement of the process for very forcing reaction conditions and particular substitution patterns on the starting materials.…”

Developments in the Chemistry of α‐Carbonyl Alkyl Bromides

“…Transition‐metal‐catalyzed functionalization reactions of alkynes have received much attention because they enable the insertion of alkyne C≡C triple bonds into C−H bonds of organic precursors, resulting in the formation of synthetically useful alkenes with regio‐ and stereoselectively –…”

“…Among the useful methods for the construction of heterocycles, the transition‐metal‐catalyzed annulation of 1, n ‐enynes with other units represents one of the most straightforward and frequently utilized approaches because of its unparalleled efficiency, high atom economy, and step economy –…”

Cooperative Palladium and Copper Catalysis: One‐pot Synthesis of Diamino‐Substituted Naphthalenes from Aryl Halides, 1,4‐Bis(trimethylsilyl)butadiyne and Amines

“…Polycyclic aromatic hydrocarbons (PAHs) are an important class of organic conjugated molecules, which are widely used for luminescent materials and molecular devices because of their fascinating optical and electronic properties . Development of a new synthetic route to aromatic cores is crucial for obtaining functionalized PAHs .…”