Benzannulation Reactions: A Case for Perspective Change From Arene Decoration to Arene Construction

Abstract

Benzannulation reactions involve construction of a benzene ring from acyclic precursors. This class of reactions offer a versatile and often superior alternative to aromatic substitution for construction of substituted arenes. Selected pioneering and recent reports of various benzannulation reactions are categorised and discussed in this review.

Polyarylquinone Synthesis by Relayed Dehydrogenative [2 + 2 + 2] Cycloaddition

“…More than the ability to precisely control the molecular structure, the synthetic challenges associated with integrating contiguous conjugated double bonds, in accurate locations, in a strained cyclic structure have caught the attention of synthetic chemists. Efforts toward constructing high order molecular polyarenes have led to multistep synthetic plans involving key transformations such as the Diels–Alder cycloaddition, cyclotrimerization, or cross-coupling . It can be noted that mostly cycloadditions using Pd, Rh, Ru, Re, Co, or Mn catalysts have been used to install individual benzene/heteroarene rings by reactions between alkynes and alkenes, alkynes and benzynes or allenes, alkynes and ketones or β-keto esters, alkynes and enol ethers, alkynes and imines, alkynes and nitriles, and between alkenes .…”

Ru(II)-Catalyzed Deoxygenative Formal [3 + 1 + 2] Benzannulation of Allyl Alcohols and Acetylenediesters via C–H Activation and Selective Carbon–Carbon Triple Bond Cleavage

“…T he development of convenient and efficient synthetic methods to construct highly substituted aromatic compounds has received extensive interest due to their ubiquitous identity in various bioactive natural products (Figure 1), 1 pharmaceuticals, 2 and agrochemicals. 3 They are also used as building blocks for preparation of versatile industrial chemicals, biomedical products, and advanced functional materials. 4 The identity and flexible substitution patterns on the benzene ring directly determine the functional behavior of the benzene-ring-containing molecules.…”

Divergent Approach to Highly Substituted Arenes via [3 + 3] Annulation of Vinyl Sulfoxonium Ylides with Ynones

“…The properties of the arene-containing molecules are determined by the substitution pattern as well as the type of substituents installed on the arene unit . Since the last few decades, much effort has been devoted to constructing polysubstituted arenes using various catalysts and reagents. , Despite these approaches, to the best of our knowledge, there has been no report on the catalyst- and reagent-free benzannulation for polysubstituted arenes under mild conditions.…”