Regioselective Synthesis of Substituted Arenes via Aerobic Oxidative [3 + 3] Benzannulation Reactions of α,β-Unsaturated Aldehydes and Ketones

Abstract

Facile conversion of α,β-unsaturated aldehydes and ketones into highly substituted arenes via a base-mediated, completely regioselective, air-oxidative [3 + 3] benzannulation reaction with readily available 4-sulfonylcrotonates or 1,3-bisphenylsulfonylpropene is reported. The reaction can also be carried out as a one-pot, three-component operation using 4-bromocrotonates, aryl sulfinates, and cinnamaldehyde. This open-flask, metal-free reaction does not require anhydrous solvents, proceeds under mild conditions, and uses atmospheric oxygen as the oxidant to afford high yields of the 3-(arylsulfonyl)benzoic acid esters.

Facile synthesis of 4H-chromene derivatives via base-mediated annulation of ortho-hydroxychalcones and 2-bromoallyl sulfones

“…During the course of our recent investigations on annulation reactions of unsaturated sulfones [ 16 – 17 ], we became interested in the possibility of exploiting allenyl sulfones as a building block for heterocyclic sulfones. The synthetic potential of allenyl sulfones remains largely unexploited.…”

Recent Advances in Organocatalyst‐Mediated Benzannulation Reactions

“…In 2015, Singarapu and Menon reported a DBU-mediated benzannulation reaction of 4-sulfonylcrotonates 70 and α,β-unsaturated aldehydes 71 by an aerobic oxidative (3 + 3) annulation strategy. [38] Further study showed that the symmetric 1,3-bisphenylsulfonyl propene also acted as the nucleophilic 1,3-dipolar synthon in the benzannulation reaction, affording the 2,4-bis(phenyl-sulfonyl)biphenyl in good yield (Scheme 14a). It was noted that this benzannulation reaction could be carried out conveniently as a one-pot procedure using commercially available sulfinate salt, 4-bromocrotonate, and cinnamaldehyde.…”

Recent Progress in Transition‐Metal‐Free, Base‐Mediated Benzannulation Reactions for the Synthesis of a Diverse Range of Aromatic and Heteroaromatic Compounds

“…Previously, Joshi et al. developed a DBU‐mediated aerobic oxidative [3+3] benzannulation reaction of 4‐sulfonylcrotonates 202 with α,β‐unsaturated aldehydes and ketones 203 to access highly substituted aryl sulfones 204 (Scheme ) . One of the main attractive features of this method was its mild reaction conditions, which utilized atmospheric oxygen as an oxidant to afford high yields of the 3‐(arylsulfonyl)benzoic acid esters.…”